Yocheved S. answered 08/24/20
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Conjugate = 9 - 3i
(9 + 3i) • (9 - 3i) = (9)(9) + (9)(-3i) + (3i)(9) + (3i)(-3i) = 81 - 27i + 27i - 9i2 = 81 + 9 = 90