x^2 + y^2 = 25
2x + y = -5.....y = -2x - 5
x^2 + (-2x - 5)^2 = 25
x^2 + (-2x - 5)(-2x - 5) = 25
x^2 + (4x^2 + 20x + 25) = 25
5x^2 + 20x + 25 = 25
5x^2 + 20x = 0
5x(x + 4) = 0
5x = 0 2(0) + y = -5
x = 0 y = -5
x + 4 = 0 2(-4) + y = -5
x = -4 -8 + y = -5
y = 3
solutions are : x = 0, y = -5.....and x = -4, y = 3
