What must be added to the expression x\(^2\) – 18x to make it a perfect square?
- 3
- 9
- 36
- 72
-
81
The correct answer is: E
Explanation
x\(^2\) - 18x to be a perfect square.
\((\frac{b}{2})^2\) is added to ax\(^2\) + bx + c in order to make it a perfect square.
\(x^2 - 18x + (\frac{-18}{2})^2\)
= \(x^2 - 18x + 81\)