Complex numbers have a real and imaginary part: z = a + bi.
Addition: (a+bi) + (c+di) = (a+c) + (b+d)i.
Multiplication: (a+bi)(c+di) = (ac−bd) + (ad+bc)i.
Modulus: |z| = √(a²+b²).
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A complex number has a real part (a) and imaginary part (bi), written as a + bi.
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