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

The correct answer is E. 81

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.

\(x^2 - 18x + (\frac{-18}{2})^2\)

= \(x^2 - 18x + 81\)

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