What must be added to the expression x 2 - 18x to make it a
MATHEMATICS
WAEC 1992
What must be added to the expression x2 - 18x to make it a perfect square?
- A. 3
- B. 9
- C. 36
- D. 81
Correct Answer: D. 81
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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