X^2 + y^2=40 and y=x-4 solve this simultaneous equation

Write x-4 instead of y.
x²+(x-4)²=40
x²+x²-8x+16=40
2x²-8x-24=0
x²-4x-12=0
(x-6)(x+2)=0
x=6 or x=-2

for x=6, y=6-4 = 2
for x=-2, y=-2-4 = -6

Bis the correct answer

Is it multiple choice