Algebra 2 Intermediate

Simplifying Complex Numbers

Write complex expressions in standard form a + bi — simplify powers of i, square roots of negative numbers, and combined expressions.

Live Calculator · Step-by-Step · Algebra 2
Input
Computes in in a+bi form using the i-cycle (period 4).
Examples
Computes √n where n < 0. Simplifies the radical and writes result as bi.
Examples
Enter expressions with i, i^n, sqrt(-n). Use ^ for powers.
Examples
Result in a + bi Form
Select a mode, enter your expression, and press Simplify to see the result in standard a + bi form.
Standard Form
0
a  (Real Part)
0
b  (Imaginary Part)
i-cycle reference
i¹ = i
i² = −1
i³ = −i
i⁴ = 1
Step-by-Step Solution
Powers of i — Period-4 Cycle
i¹ = i  |  i² = −1  |  i³ = −i  |  i⁴ = 1

The powers of i repeat with period 4. To find in for any integer n, compute n mod 4:

n mod 4 = 0 → i⁴ = 1  |  n mod 4 = 1 → i¹ = i

n mod 4 = 2 → i² = −1  |  n mod 4 = 3 → i³ = −i

Example: i¹⁵ → 15 mod 4 = 3 → i³ = −i

For negative exponents: i⁻¹ = −i, i⁻² = −1, i⁻³ = i, i⁻⁴ = 1 (same cycle, same rule applies).
Square Roots of Negatives & Standard Form
√(−a) = i√a  for a > 0

A complex number in standard form is a + bi where:

a = real part  |  b = imaginary part  |  i = √(−1)

To simplify √(−n): factor out √(−1) = i, then simplify √n by pulling out perfect square factors.

Example: √(−12) = i√12 = i√(4·3) = 2i√3

  • Replace every i² with −1 when simplifying.
  • Combine all real terms; combine all imaginary terms.
  • Write answer as a + bi with real part first.
  • If b = 0, the result is purely real.

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