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
Correct Answer: Option 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)