-3x + y = 4
Solve for y
y = 3x + 4
Plug this y value into the other equation.
-9x + 5y = -1
-9x + 5(3x + 4) = -1
Distribute 5(3x + 4)
-9x + 15x + 20 = -1
Subtract 20 from both sides
-9x + 15x + 20 - 20 = -1 - 20
-9x + 15x = -21
Combine like terms
6x = -21
Divide both sides by 6
6/6 x = -21/6
1x = -21/6
x = -7/2
x = -3.5 or -7/2
Plug this value into an equation to solve for y.
-3(-3.5) + y = 4
10.5 + y = 4
Subtract both sides by 10.5
10.5 - 10.5 + y = 4 - 10.5
y = -6.5
Check this answer by plugging the value of x into the other equation.
-9(-3.5) + 5y = -1
31.5 + 5y = -1
Subtract both sides by 31.5
31.5 - 31.5 + 5y = -1 - 31.5
5y = -32.5
Divide both sides by 5
y = -6.5 or -13/2
Therefore the solution is ( -3.5 , -6.5 )
