Equation 1) -3x + 9y = 45
Equation 2) y = -x - 1
Add x to both sides on equation 2.
2) x + y = -1
1) -3x + 9y = 45
Multiply ALL of equation 2 by 3.
2) 3(x + y = -1)
Simplify.
2) 3x + 3y = -3
1) -3x + 9y = 45
Add equations together.
12y = 42
Divide both sides with 12.
y = 3.5
Plug in 3.5 for y in the first equation.
-3x + 9y = 45
-3x + 9(3.5) = 45
Simplify.
-3x + 31.5 = 45
Subtract 31.5 from both sides.
-3x = 45 - 31.5
Simplify.
-3x = 13.5
Divide both sides by -3.
x = -4.5
(-4.5, 3.5)
~Hope I helped!~