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

What must be added to the expression x\(^2\) - 18x to make it a perfect square?
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  • 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.
\(x^2 - 18x + (\frac{-18}{2})^2\)
= \(x^2 - 18x + 81\)

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