Answer:
i2 - 9
-85
Step-by-step explanation:
Conjugate of an expression is gotten by simply changing the sign to the opposite sign. For example, the conjugate of 5 is -5, the conjugate of x+2 is x-2. Given the complex value 2i+9, the conjugate will be -85
Taking their product
(2i+9)(2i-9)
Expand
2i(2i)-9(2i)+9(2i)+9(-9)
= 4i²-18-+18i-81
= 4i² - 81
Since i² = -1
= 4(-1) - 81
= -4-81
= -85
Hence the product will give -85
