Can you help me solve this algebra problem?
$begingroup$
Hi I need to solve this problem and I don’t know how. I’d appreciate your help.
If $x - frac{ayz}{x^2} = y - frac{azx}{y^2} = z - frac{axy}{z^2}$ and $xneq yneq z$, then $$x - frac{ayz}{x^2} = y - frac{azx}{y^2} = z - frac{axy}{z^2} = x + y + z - a$$
I think I need to
$x^3 - ayz = x^2k$
$y^3 - azx = y^2k,$
$z^3 - axy = z^2k$
then to multiply both sides of each equality by some quantity, add them all together and factor but I don’t know how to find that quantity.
algebra-precalculus systems-of-equations
$endgroup$
add a comment |
$begingroup$
Hi I need to solve this problem and I don’t know how. I’d appreciate your help.
If $x - frac{ayz}{x^2} = y - frac{azx}{y^2} = z - frac{axy}{z^2}$ and $xneq yneq z$, then $$x - frac{ayz}{x^2} = y - frac{azx}{y^2} = z - frac{axy}{z^2} = x + y + z - a$$
I think I need to
$x^3 - ayz = x^2k$
$y^3 - azx = y^2k,$
$z^3 - axy = z^2k$
then to multiply both sides of each equality by some quantity, add them all together and factor but I don’t know how to find that quantity.
algebra-precalculus systems-of-equations
$endgroup$
$begingroup$
Are you trying to prove the last equality? It's not clear.
$endgroup$
– Victor S.
8 hours ago
$begingroup$
@VictorS. I need to prove that each expression is equal to x + y + z - a
$endgroup$
– questions about math
8 hours ago
$begingroup$
This isn't an answer. However, it could help... $$$$Observe that $$(x+y+z-a)-bigg(x-frac{ayz}{x^2}bigg)=frac{ayz+yx^2+zx^2-ax^2}{x^2}=frac{a(yz-x^2)+x^2(y+z)}{x^2}$$ This equals zero iff $$a(x^2-yz)=x^2(y+z)iff a-frac{ayz}{x^2}=y+z$$ $$iff a·bigg(frac{x^2-yz}{x^2}bigg)=y+ziff a=frac{x^2y+x^2z}{x^2-yz}$$
$endgroup$
– Dr. Mathva
6 hours ago
add a comment |
$begingroup$
Hi I need to solve this problem and I don’t know how. I’d appreciate your help.
If $x - frac{ayz}{x^2} = y - frac{azx}{y^2} = z - frac{axy}{z^2}$ and $xneq yneq z$, then $$x - frac{ayz}{x^2} = y - frac{azx}{y^2} = z - frac{axy}{z^2} = x + y + z - a$$
I think I need to
$x^3 - ayz = x^2k$
$y^3 - azx = y^2k,$
$z^3 - axy = z^2k$
then to multiply both sides of each equality by some quantity, add them all together and factor but I don’t know how to find that quantity.
algebra-precalculus systems-of-equations
$endgroup$
Hi I need to solve this problem and I don’t know how. I’d appreciate your help.
If $x - frac{ayz}{x^2} = y - frac{azx}{y^2} = z - frac{axy}{z^2}$ and $xneq yneq z$, then $$x - frac{ayz}{x^2} = y - frac{azx}{y^2} = z - frac{axy}{z^2} = x + y + z - a$$
I think I need to
$x^3 - ayz = x^2k$
$y^3 - azx = y^2k,$
$z^3 - axy = z^2k$
then to multiply both sides of each equality by some quantity, add them all together and factor but I don’t know how to find that quantity.
algebra-precalculus systems-of-equations
algebra-precalculus systems-of-equations
edited 5 hours ago
Michael Rozenberg
105k1892197
105k1892197
asked 8 hours ago
questions about mathquestions about math
714
714
$begingroup$
Are you trying to prove the last equality? It's not clear.
$endgroup$
– Victor S.
8 hours ago
$begingroup$
@VictorS. I need to prove that each expression is equal to x + y + z - a
$endgroup$
– questions about math
8 hours ago
$begingroup$
This isn't an answer. However, it could help... $$$$Observe that $$(x+y+z-a)-bigg(x-frac{ayz}{x^2}bigg)=frac{ayz+yx^2+zx^2-ax^2}{x^2}=frac{a(yz-x^2)+x^2(y+z)}{x^2}$$ This equals zero iff $$a(x^2-yz)=x^2(y+z)iff a-frac{ayz}{x^2}=y+z$$ $$iff a·bigg(frac{x^2-yz}{x^2}bigg)=y+ziff a=frac{x^2y+x^2z}{x^2-yz}$$
$endgroup$
– Dr. Mathva
6 hours ago
add a comment |
$begingroup$
Are you trying to prove the last equality? It's not clear.
$endgroup$
– Victor S.
8 hours ago
$begingroup$
@VictorS. I need to prove that each expression is equal to x + y + z - a
$endgroup$
– questions about math
8 hours ago
$begingroup$
This isn't an answer. However, it could help... $$$$Observe that $$(x+y+z-a)-bigg(x-frac{ayz}{x^2}bigg)=frac{ayz+yx^2+zx^2-ax^2}{x^2}=frac{a(yz-x^2)+x^2(y+z)}{x^2}$$ This equals zero iff $$a(x^2-yz)=x^2(y+z)iff a-frac{ayz}{x^2}=y+z$$ $$iff a·bigg(frac{x^2-yz}{x^2}bigg)=y+ziff a=frac{x^2y+x^2z}{x^2-yz}$$
$endgroup$
– Dr. Mathva
6 hours ago
$begingroup$
Are you trying to prove the last equality? It's not clear.
$endgroup$
– Victor S.
8 hours ago
$begingroup$
Are you trying to prove the last equality? It's not clear.
$endgroup$
– Victor S.
8 hours ago
$begingroup$
@VictorS. I need to prove that each expression is equal to x + y + z - a
$endgroup$
– questions about math
8 hours ago
$begingroup$
@VictorS. I need to prove that each expression is equal to x + y + z - a
$endgroup$
– questions about math
8 hours ago
$begingroup$
This isn't an answer. However, it could help... $$$$Observe that $$(x+y+z-a)-bigg(x-frac{ayz}{x^2}bigg)=frac{ayz+yx^2+zx^2-ax^2}{x^2}=frac{a(yz-x^2)+x^2(y+z)}{x^2}$$ This equals zero iff $$a(x^2-yz)=x^2(y+z)iff a-frac{ayz}{x^2}=y+z$$ $$iff a·bigg(frac{x^2-yz}{x^2}bigg)=y+ziff a=frac{x^2y+x^2z}{x^2-yz}$$
$endgroup$
– Dr. Mathva
6 hours ago
$begingroup$
This isn't an answer. However, it could help... $$$$Observe that $$(x+y+z-a)-bigg(x-frac{ayz}{x^2}bigg)=frac{ayz+yx^2+zx^2-ax^2}{x^2}=frac{a(yz-x^2)+x^2(y+z)}{x^2}$$ This equals zero iff $$a(x^2-yz)=x^2(y+z)iff a-frac{ayz}{x^2}=y+z$$ $$iff a·bigg(frac{x^2-yz}{x^2}bigg)=y+ziff a=frac{x^2y+x^2z}{x^2-yz}$$
$endgroup$
– Dr. Mathva
6 hours ago
add a comment |
2 Answers
2
active
oldest
votes
$begingroup$
$$x-frac{ayz}{x^2}=y-frac{axz}{y^2}$$ gives
$$x-y+azleft(frac{x}{y^2}-frac{y}{x^2}right)=0$$ or
$$1+frac{az(x^2+xy+y^2)}{x^2y^2}=0.$$
Similarly, $$frac{ax(y^2+yz+z^2)}{y^2z^2}=-1$$ and
$$frac{ay(x^2+xz+z^2)}{x^2z^2}=-1.$$
Thus, $$x^3(y^2+yz+z^2)=y^3(x^2+xz+z^2)$$ or
$$(x-y)(x^2y^2+xyz(x+y)+z^2(x^2+xy+y^2))=0$$ or
$$sum_{cyc}(x^2y^2+x^2yz)=0$$ or
$$sum_{cyc}z^2(x+y)^2=0,$$ which gives $$x+y=x+z=y+z=0$$ or
$$x=y=z=0,$$ which is impossible.
Id est, the given is wrong, which says that
$$x - frac{ayz}{x^2} = y - frac{azx}{y^2} = z - frac{axy}{z^2}Rightarrow x - frac{ayz}{x^2} = y - frac{azx}{y^2} = z - frac{axy}{z^2} = x + y + z - a$$ is true.
$endgroup$
$begingroup$
So, taking into account Song's answer, does this mean that the premise of the question is wrong, but if we were to ignore that then the conclusion is correct?
$endgroup$
– Marwan Mizuri
3 hours ago
1
$begingroup$
@Marwan Mizuri The Song's answer is beautiful with assuming that these $x$, $y$ and $z$ there are exist. But it's not so.
$endgroup$
– Michael Rozenberg
3 hours ago
add a comment |
$begingroup$
Denote $k=xyz$ and $b$ the common value of $x-frac{ayz}{x^2}=y-frac{azx}{y^2}=z-frac{axy}{z^2}$. We can see that the equation
$$
t-frac{ak}{t^3}=btag{*}
$$ is satisfied by $t=x,y,z$. Hence $x,y,z$ are distinct, non-zero roots of $(*)$. Note that $(*)$ can be written as a polynomial equation of degree 4
$$
t^4-b t^3-ak=0.
$$ By Vieta's formula, the other root $w$ satisfies
$$
x+y+z+w=b,quad xyzw=-ak.
$$ Since $k=xyzne 0$ it follows that
$$
w=-a=b-x-y-z,
$$ hence we get
$$
x-frac{ayz}{x^2}= y-frac{azx}{y^2}=z-frac{axy}{z^2}=b=x+y+z-a.
$$
$endgroup$
add a comment |
Your Answer
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
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votes
$begingroup$
$$x-frac{ayz}{x^2}=y-frac{axz}{y^2}$$ gives
$$x-y+azleft(frac{x}{y^2}-frac{y}{x^2}right)=0$$ or
$$1+frac{az(x^2+xy+y^2)}{x^2y^2}=0.$$
Similarly, $$frac{ax(y^2+yz+z^2)}{y^2z^2}=-1$$ and
$$frac{ay(x^2+xz+z^2)}{x^2z^2}=-1.$$
Thus, $$x^3(y^2+yz+z^2)=y^3(x^2+xz+z^2)$$ or
$$(x-y)(x^2y^2+xyz(x+y)+z^2(x^2+xy+y^2))=0$$ or
$$sum_{cyc}(x^2y^2+x^2yz)=0$$ or
$$sum_{cyc}z^2(x+y)^2=0,$$ which gives $$x+y=x+z=y+z=0$$ or
$$x=y=z=0,$$ which is impossible.
Id est, the given is wrong, which says that
$$x - frac{ayz}{x^2} = y - frac{azx}{y^2} = z - frac{axy}{z^2}Rightarrow x - frac{ayz}{x^2} = y - frac{azx}{y^2} = z - frac{axy}{z^2} = x + y + z - a$$ is true.
$endgroup$
$begingroup$
So, taking into account Song's answer, does this mean that the premise of the question is wrong, but if we were to ignore that then the conclusion is correct?
$endgroup$
– Marwan Mizuri
3 hours ago
1
$begingroup$
@Marwan Mizuri The Song's answer is beautiful with assuming that these $x$, $y$ and $z$ there are exist. But it's not so.
$endgroup$
– Michael Rozenberg
3 hours ago
add a comment |
$begingroup$
$$x-frac{ayz}{x^2}=y-frac{axz}{y^2}$$ gives
$$x-y+azleft(frac{x}{y^2}-frac{y}{x^2}right)=0$$ or
$$1+frac{az(x^2+xy+y^2)}{x^2y^2}=0.$$
Similarly, $$frac{ax(y^2+yz+z^2)}{y^2z^2}=-1$$ and
$$frac{ay(x^2+xz+z^2)}{x^2z^2}=-1.$$
Thus, $$x^3(y^2+yz+z^2)=y^3(x^2+xz+z^2)$$ or
$$(x-y)(x^2y^2+xyz(x+y)+z^2(x^2+xy+y^2))=0$$ or
$$sum_{cyc}(x^2y^2+x^2yz)=0$$ or
$$sum_{cyc}z^2(x+y)^2=0,$$ which gives $$x+y=x+z=y+z=0$$ or
$$x=y=z=0,$$ which is impossible.
Id est, the given is wrong, which says that
$$x - frac{ayz}{x^2} = y - frac{azx}{y^2} = z - frac{axy}{z^2}Rightarrow x - frac{ayz}{x^2} = y - frac{azx}{y^2} = z - frac{axy}{z^2} = x + y + z - a$$ is true.
$endgroup$
$begingroup$
So, taking into account Song's answer, does this mean that the premise of the question is wrong, but if we were to ignore that then the conclusion is correct?
$endgroup$
– Marwan Mizuri
3 hours ago
1
$begingroup$
@Marwan Mizuri The Song's answer is beautiful with assuming that these $x$, $y$ and $z$ there are exist. But it's not so.
$endgroup$
– Michael Rozenberg
3 hours ago
add a comment |
$begingroup$
$$x-frac{ayz}{x^2}=y-frac{axz}{y^2}$$ gives
$$x-y+azleft(frac{x}{y^2}-frac{y}{x^2}right)=0$$ or
$$1+frac{az(x^2+xy+y^2)}{x^2y^2}=0.$$
Similarly, $$frac{ax(y^2+yz+z^2)}{y^2z^2}=-1$$ and
$$frac{ay(x^2+xz+z^2)}{x^2z^2}=-1.$$
Thus, $$x^3(y^2+yz+z^2)=y^3(x^2+xz+z^2)$$ or
$$(x-y)(x^2y^2+xyz(x+y)+z^2(x^2+xy+y^2))=0$$ or
$$sum_{cyc}(x^2y^2+x^2yz)=0$$ or
$$sum_{cyc}z^2(x+y)^2=0,$$ which gives $$x+y=x+z=y+z=0$$ or
$$x=y=z=0,$$ which is impossible.
Id est, the given is wrong, which says that
$$x - frac{ayz}{x^2} = y - frac{azx}{y^2} = z - frac{axy}{z^2}Rightarrow x - frac{ayz}{x^2} = y - frac{azx}{y^2} = z - frac{axy}{z^2} = x + y + z - a$$ is true.
$endgroup$
$$x-frac{ayz}{x^2}=y-frac{axz}{y^2}$$ gives
$$x-y+azleft(frac{x}{y^2}-frac{y}{x^2}right)=0$$ or
$$1+frac{az(x^2+xy+y^2)}{x^2y^2}=0.$$
Similarly, $$frac{ax(y^2+yz+z^2)}{y^2z^2}=-1$$ and
$$frac{ay(x^2+xz+z^2)}{x^2z^2}=-1.$$
Thus, $$x^3(y^2+yz+z^2)=y^3(x^2+xz+z^2)$$ or
$$(x-y)(x^2y^2+xyz(x+y)+z^2(x^2+xy+y^2))=0$$ or
$$sum_{cyc}(x^2y^2+x^2yz)=0$$ or
$$sum_{cyc}z^2(x+y)^2=0,$$ which gives $$x+y=x+z=y+z=0$$ or
$$x=y=z=0,$$ which is impossible.
Id est, the given is wrong, which says that
$$x - frac{ayz}{x^2} = y - frac{azx}{y^2} = z - frac{axy}{z^2}Rightarrow x - frac{ayz}{x^2} = y - frac{azx}{y^2} = z - frac{axy}{z^2} = x + y + z - a$$ is true.
answered 5 hours ago
Michael RozenbergMichael Rozenberg
105k1892197
105k1892197
$begingroup$
So, taking into account Song's answer, does this mean that the premise of the question is wrong, but if we were to ignore that then the conclusion is correct?
$endgroup$
– Marwan Mizuri
3 hours ago
1
$begingroup$
@Marwan Mizuri The Song's answer is beautiful with assuming that these $x$, $y$ and $z$ there are exist. But it's not so.
$endgroup$
– Michael Rozenberg
3 hours ago
add a comment |
$begingroup$
So, taking into account Song's answer, does this mean that the premise of the question is wrong, but if we were to ignore that then the conclusion is correct?
$endgroup$
– Marwan Mizuri
3 hours ago
1
$begingroup$
@Marwan Mizuri The Song's answer is beautiful with assuming that these $x$, $y$ and $z$ there are exist. But it's not so.
$endgroup$
– Michael Rozenberg
3 hours ago
$begingroup$
So, taking into account Song's answer, does this mean that the premise of the question is wrong, but if we were to ignore that then the conclusion is correct?
$endgroup$
– Marwan Mizuri
3 hours ago
$begingroup$
So, taking into account Song's answer, does this mean that the premise of the question is wrong, but if we were to ignore that then the conclusion is correct?
$endgroup$
– Marwan Mizuri
3 hours ago
1
1
$begingroup$
@Marwan Mizuri The Song's answer is beautiful with assuming that these $x$, $y$ and $z$ there are exist. But it's not so.
$endgroup$
– Michael Rozenberg
3 hours ago
$begingroup$
@Marwan Mizuri The Song's answer is beautiful with assuming that these $x$, $y$ and $z$ there are exist. But it's not so.
$endgroup$
– Michael Rozenberg
3 hours ago
add a comment |
$begingroup$
Denote $k=xyz$ and $b$ the common value of $x-frac{ayz}{x^2}=y-frac{azx}{y^2}=z-frac{axy}{z^2}$. We can see that the equation
$$
t-frac{ak}{t^3}=btag{*}
$$ is satisfied by $t=x,y,z$. Hence $x,y,z$ are distinct, non-zero roots of $(*)$. Note that $(*)$ can be written as a polynomial equation of degree 4
$$
t^4-b t^3-ak=0.
$$ By Vieta's formula, the other root $w$ satisfies
$$
x+y+z+w=b,quad xyzw=-ak.
$$ Since $k=xyzne 0$ it follows that
$$
w=-a=b-x-y-z,
$$ hence we get
$$
x-frac{ayz}{x^2}= y-frac{azx}{y^2}=z-frac{axy}{z^2}=b=x+y+z-a.
$$
$endgroup$
add a comment |
$begingroup$
Denote $k=xyz$ and $b$ the common value of $x-frac{ayz}{x^2}=y-frac{azx}{y^2}=z-frac{axy}{z^2}$. We can see that the equation
$$
t-frac{ak}{t^3}=btag{*}
$$ is satisfied by $t=x,y,z$. Hence $x,y,z$ are distinct, non-zero roots of $(*)$. Note that $(*)$ can be written as a polynomial equation of degree 4
$$
t^4-b t^3-ak=0.
$$ By Vieta's formula, the other root $w$ satisfies
$$
x+y+z+w=b,quad xyzw=-ak.
$$ Since $k=xyzne 0$ it follows that
$$
w=-a=b-x-y-z,
$$ hence we get
$$
x-frac{ayz}{x^2}= y-frac{azx}{y^2}=z-frac{axy}{z^2}=b=x+y+z-a.
$$
$endgroup$
add a comment |
$begingroup$
Denote $k=xyz$ and $b$ the common value of $x-frac{ayz}{x^2}=y-frac{azx}{y^2}=z-frac{axy}{z^2}$. We can see that the equation
$$
t-frac{ak}{t^3}=btag{*}
$$ is satisfied by $t=x,y,z$. Hence $x,y,z$ are distinct, non-zero roots of $(*)$. Note that $(*)$ can be written as a polynomial equation of degree 4
$$
t^4-b t^3-ak=0.
$$ By Vieta's formula, the other root $w$ satisfies
$$
x+y+z+w=b,quad xyzw=-ak.
$$ Since $k=xyzne 0$ it follows that
$$
w=-a=b-x-y-z,
$$ hence we get
$$
x-frac{ayz}{x^2}= y-frac{azx}{y^2}=z-frac{axy}{z^2}=b=x+y+z-a.
$$
$endgroup$
Denote $k=xyz$ and $b$ the common value of $x-frac{ayz}{x^2}=y-frac{azx}{y^2}=z-frac{axy}{z^2}$. We can see that the equation
$$
t-frac{ak}{t^3}=btag{*}
$$ is satisfied by $t=x,y,z$. Hence $x,y,z$ are distinct, non-zero roots of $(*)$. Note that $(*)$ can be written as a polynomial equation of degree 4
$$
t^4-b t^3-ak=0.
$$ By Vieta's formula, the other root $w$ satisfies
$$
x+y+z+w=b,quad xyzw=-ak.
$$ Since $k=xyzne 0$ it follows that
$$
w=-a=b-x-y-z,
$$ hence we get
$$
x-frac{ayz}{x^2}= y-frac{azx}{y^2}=z-frac{axy}{z^2}=b=x+y+z-a.
$$
edited 4 hours ago
answered 5 hours ago
SongSong
14.5k1635
14.5k1635
add a comment |
add a comment |
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Are you trying to prove the last equality? It's not clear.
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– Victor S.
8 hours ago
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@VictorS. I need to prove that each expression is equal to x + y + z - a
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– questions about math
8 hours ago
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This isn't an answer. However, it could help... $$$$Observe that $$(x+y+z-a)-bigg(x-frac{ayz}{x^2}bigg)=frac{ayz+yx^2+zx^2-ax^2}{x^2}=frac{a(yz-x^2)+x^2(y+z)}{x^2}$$ This equals zero iff $$a(x^2-yz)=x^2(y+z)iff a-frac{ayz}{x^2}=y+z$$ $$iff a·bigg(frac{x^2-yz}{x^2}bigg)=y+ziff a=frac{x^2y+x^2z}{x^2-yz}$$
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– Dr. Mathva
6 hours ago