Mathematics
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OpenStudy (anonymous):
solve the system the first equation is 3xy-4(x^2)=2 and the second equation is -5(x^2)+3y^2=7
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OpenStudy (anonymous):
\[{3xy-4x^2=2,- 5x^2+3y^2=7}\]
OpenStudy (anonymous):
i need to know how to solve it for all its real solutions
OpenStudy (mertsj):
Solve the first equation for y and substitute into the second equation.
OpenStudy (anonymous):
yeah but there are 4 solutions
OpenStudy (mertsj):
Yes. And when you do that you will get an equation containing x^4 which will have 4 solutions.
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OpenStudy (anonymous):
ok
OpenStudy (mertsj):
\[y=\frac{2+4x^2}{3x}\]
OpenStudy (mertsj):
Substitute that into the second equation.
OpenStudy (anonymous):
so i just solve that
OpenStudy (mertsj):
Do you know what substitute means?
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OpenStudy (anonymous):
ok yes got it
OpenStudy (mertsj):
\[-5x^2+3(\frac{2+4x^2}{3x})^2=7\]
OpenStudy (mertsj):
\[-5x^2+3(\frac{4+16x^2+16x^4}{9x^2})=7\]
OpenStudy (anonymous):
ok
OpenStudy (anonymous):
i already have two solutions i just need to know how to get the other two
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OpenStudy (mertsj):
\[-5x^2+\frac{12+48x^2+48x^4}{9x^2}=7\]
OpenStudy (mertsj):
What are the two you have?
OpenStudy (anonymous):
(-3,-3) and (2,3) and i know th other two are (-1,-2) and (1,20 i just don't know how to get them
OpenStudy (mertsj):
You end up with:
\[(x^2-4)(x^2-1)=0\]
OpenStudy (anonymous):
sorry the first one is (-2,-3)
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OpenStudy (mertsj):
So x = 2, -2, 1, -1
OpenStudy (mertsj):
So go back to the equation:
OpenStudy (mertsj):
\[y=\frac{2+4x^2}{3x}\]
OpenStudy (mertsj):
And replace x with each one of the 4 x values and find the corresponding y.
OpenStudy (anonymous):
k
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OpenStudy (anonymous):
so r (2,3) and (-2,-3) not solutions
OpenStudy (mertsj):
(2,6) (-2,-6) (1,2) (-1,-2)
OpenStudy (anonymous):
abc123 that is true
OpenStudy (anonymous):
what is
OpenStudy (mertsj):
That (2,3) and (-2,-3) are not solutions.
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OpenStudy (anonymous):
(2,3) and (-2,-3)
OpenStudy (anonymous):
ok
OpenStudy (anonymous):
What grade are you in bro?
OpenStudy (anonymous):
11. don't judge
OpenStudy (mertsj):
No wait. Those two are solutions. The 4 solutions are:(2,3, )(-2,-3, )(1,2), (-1,-2)
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OpenStudy (mertsj):
Sorry. I made a calculation error earlier.
OpenStudy (anonymous):
ok