Solve the simultaneous equations x^2 + y^2 = 9 and y = 3x + 3

y² = (3x + 3)² = 9x² + 18x + 9

x² + 9x² + 18x + 9 = 9

10x² + 18x = 0 (root a: x = 0)

5x + 9 = 0 (root b: x = -1.8)

For x = 0, y = 3(0) + 3 (root a: y = 3)

For x = -1.8, y = 3(-1.8) + 3 (root b: y = -2.4)

Solutions at (0, 3) and (-1.8, -2.4)