WAEC - Mathematics (1992 - No. 12)
What must be added to the expression x\(^2\) - 18x to make it a perfect square?
3
9
36
72
81
Explicació
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.
\(x^2 - 18x + (\frac{-18}{2})^2\)
= \(x^2 - 18x + 81\)