Question

what is the best method to solve 5x+4y=-7 -5x-2y=1 and why?

Answer 1

addition method is the best because we have a variable with its opposite numbers, so adding them will eliminate

so we will get Y in an instant

$\begin{gathered} 5x+4y=-7 \\ -5x-2y=1 \\ ------------ \\ 0x+2y=-6 \end{gathered}$$\begin{gathered} 2y=-6 \\ y=-3 \end{gathered}$

now, we can replace on any equation to solve x

$\begin{gathered} 5x+4(-3)=-7 \\ 5x-12=-7 \\ 5x=-7+12 \\ x=\frac{5}{5} \\ x=1 \end{gathered}$