What must be added to the expression x\(^2\) - 18x to make it a perfect square?
A
3
B
9
C
36
D
72
E
81
Verified Correct Answer: E.
Step-by-Step Mathematical Solution
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.
\(x^2 - 18x + (\frac{-18}{2})^2\)
= \(x^2 - 18x + 81\)
Source: Myschool Past Questions Archive (Record #23150)