Mathematics

What must be added to the expression x(^2) – 18x to make it a perfect square?

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)