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What is the product of the complex numbers (-3i+4) and (3i+4)?

User Tfogo
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(-3i + 4)(3i + 4)

Use the FOIL method

multiply the Firsts: -3i * 3i = -9i² = because i² = -1 ⇒ -9i² = -9(-1) = 9
multiply the Outers: -3i * 4 = -12i
multiply the Inners: 4 * 3i = 12i
multiply the lasts: 4 * 4 = 12

9 - 12i + 12i + 12 = 21
User Korwalskiy
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