how do i solve for this system of equations

11x-3y=-36

12y-9x=39

?

tried reordering the terms but what else?

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- Aug 9th 2010, 07:22 PMgabrielSystem of linear equations.
how do i solve for this system of equations

11x-3y=-36

12y-9x=39

?

tried reordering the terms but what else? - Aug 9th 2010, 07:51 PMpickslides
- Aug 9th 2010, 08:08 PMgabriel
yeppp i got thnx good refreshment to the dusty mind

- Aug 9th 2010, 10:14 PMProve It
The alternative method (the method used for more equations with more unknowns) is the elimination method...

$\displaystyle 11x - 3y = -36$

$\displaystyle -9x + 12y = 39$.

Multiply the first equation by 4 to give

$\displaystyle 44x-12y=-144$

$\displaystyle -9x+12y=39$

Add the equations together

$\displaystyle (44x-12y)+(-9x+12y)=-144+39$

$\displaystyle 35x=-105$

$\displaystyle x = -3$.

Substitute into one of the original equations...

$\displaystyle 11(- 3) - 3y = -36$

$\displaystyle -33- 3y = -36$

$\displaystyle -3y = -3$

$\displaystyle y = 1$

So the solution is $\displaystyle (x,y) = (-3,1)$. - Aug 9th 2010, 10:39 PMearboth
- Aug 9th 2010, 11:03 PMProve It
Yes I did, edited :)