Question

1.
x+3y=-1
2x+9y=7 help please

Answer 1

`x=-10`

`y=3`

Explanation:

What you have here is a system of equations. Lets modify equation (1) in order to make this easier.

Multiply equation (1) by -3:

`(-3)x+(-3)3y=(-3)(-1)`

`-3x-9y=3`

Now our two equations look like this:

`-3x-9y=3`

`2x+9y=7\\`

Notice that our y variable are now opposites. Now we can add both equations together to simply have the x variable:

`(-3x+2x)+(-9y+9y)=(3+7)`

`-x=10`

To find x, divide both sides by -1:

`x=-10`

Now plug -10 as x back into either original equation, I will do #1 because it is slightly easier:

`-10+3y=-1`

Add 10 to both sides:

`3y=9`

Divide both sides by 3:

`y=3`

Therefore we know that:

`x=-10`

`y=3`