Question

How do I solve this using elimination method. 2x+5y=-7
-3x-4y=0

Answer 1

`\left\{\begin{array}{ccc}2x+5y=-7&\text{multiply both sides by 3}\\-3x-4y=0&\text{multiply both sides by 2}\end{array}\right\\\underline{+\left\{\begin{array}{ccc}6x+15y=-21\\-6x-8y=0\end{array}\right}\qquad\text{add both sides of the equations}\\.\qquad\qquad7y=-21\qquad\text{divide both sides by 7}\\.\qquad\qquad\boxed{y=-3}\\\\\text{Put the value of y to the second equation:}\\\\-3x-4(-3)=0\\\\-3x+12=0\qquad\text{subtract 12 from both sides}\\\\-3x=-12\qquad\text{divide both sides by (-3)}\\\\\boxed{x=4}\\\\Answer:\ \boxed{x=4\ and\ y=-3\to(4,\ -3)}`