JAMB - Mathematics (1990 - No. 18)
What must be added to 4x\(^2\) - 4 to make it a perfect square?
\(\frac{-1}{x^2}\)
\(\frac{1}{x^2}\)
1
-1
Explanation
4x\(^2\) - 4 = (2x)\(^2\) - 2\(^2\)
(2x)\(^2\) - 2\(^2\) = a\(^2\) - b\(^2\) = (a - b)\(^2\) - 2ab - 2b\(^2\)
(a - b)\(^2\) = a - b\(^2\) + (2ab + 2b)\(^2\)
a = 2x and b = 2
2ab + 2b\(^2\) = 2(2x)(2) + 2(2)\(^2\) = 8x + 8 = 8(x + 1)
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