Complex Numbers Definition i = √(-1) | i² = -1 | i³ = -i | i⁴ = 1 Operations Add/Subtract: combine real and imaginary parts separately Multiply: use FOIL and replace i² with -1 Divide: multiply by conjugate of denominator Conjugate Conjugate of a + bi is a - bi (a + bi)(a - bi) = a² + b² (always real) SAT Tips Powers of i cycle every 4: i, -1, -i, 1 To find i^n: divide n by 4 and use the remainder Complex numbers appear in the "no real solutions" context