Question

Solve by substitution.2x + y = -9(3x + 5y = 4([?],[])

Answer 1

The given system is

`\mleft\{\begin{aligned}2x+y=-9 \\ 3x+5y=4\end{aligned}\mright.`

Let's isolate y in the first equation.

`\begin{gathered} 2x+y=-9 \\ y=-9-2x \end{gathered}`

Then, we replace the equation we've got in the second equation of the system.

`3x+5(-9-2x)=4`

Now, we solve for x.

`\begin{gathered} 3x-45-10x=4 \\ -7x=4+45 \\ -7x=49 \\ x=(49)/(-7) \\ x=-7 \end{gathered}`

We use this value to find y.

`\begin{gathered} y=-9-2(-7) \\ y=-9+14 \\ y=5 \end{gathered}`

Therefore, the solutions are x = -7 and y = 5.