I assume you want the equation to be solved, so this is a quadratic simultaneous equation.
y = x^2-x-3 ——— (1)
y = -3x+5 ——— (2)
Sub (1) into (2)
(This is the first three steps provided)
x^2-x-3 = -3x+5
0 = x^2+2x-8
0 = (x-2)(x+4) ——— (3)
Solve for x in (3):
x-2 = 0
x = 2
x+4 = 0
x = -4
Sub x into (2)
y = -3(2) + 5
y = -1
y = -3(-4) + 5
y = 17
Hence the solution sets are:
x=2, y=-1
x=-4, y=17
