1.3 Multiplying and Divide Complex Numbers Quiz: Thursday

Vocabulary To multiply two complex numbers, use the FOIL method. –REMEMBER: i 2 = -1 Two complex numbers of the form (a + bi) and (a – bi) are called complex conjugates. –The product of complex conjugates is always a real number. –Ex: (2 + 4i)(2 – 4i) = 4 – 8i + 8i + 16 = 20

Vocabulary Complex Conjugates –You can use this fact to divide complex numbers. –When a quotient has an imaginary number in the denominator, multiply by the conjugate so that you have a real number in the denominator. –Ex: what would we multiply by to get rid of the imaginary # in the denominator?

Example 1: Multiply the complex conjugates 1.(4 + 3i)(4 – 3i) 2.(8 – 4i)(8 + 4i)

Example 2: Write the expression as a complex number in standard form. 1.4i(6 + 2i) 2.(3 – 2i)(-1 + 4i) 3.(5 + 7i)(2 + i)

Example 3: Write the expression as a complex number in standard form.

You Try: Write the expression as a complex number in standard form.

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