Question

Solve the following pair of linear equations by the elimination method and the subsitution method:
$3x-5y-4=0$ and $9x=2y+7$

Answer 1

$3(3x-5y=4)\Rightarrow 9x-15y=12$

$9x-2y=7$ $\Rightarrow 9x-2y=7$

___________

$-13y=5$

$y=\frac{-5}{13}$

$x=\frac{-10/13+7}{9}=\frac{9}{13}$

Substitution method

$3x=5y+4$

$3.(5y+4)=2y+7$ $\Rightarrow 15y+12=2y+7$

$\Rightarrow 13y=-5\Rightarrow y=\frac{-5}{13}$

$x=\frac{-10/13+7}{9}=\frac{9}{13}$