Two complex numbers multiplied to become a real number

A complex number is a special type of number that takes the form of a + bi, where i is the symbol for the square root of -1. Can you figure out two complex numbers (where neither a nor b is zero) that when multiplied together become a real number? 

(2 + i)(2 - i) {two complex numbers}
= 2(2) + 2(-i) + i(2) + i(-i) {used foil method}
= 4 - 2i + 2i - i² {multiplied through}
= 4 - i² {combined like terms}
= 4 - (-1) {i² is -1}
= 4 + 1 {simplified double negative signs}
= 5 {added}

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