Question
Factorise: $4a^2- 9$
✓
Answer
$4a^2- 9$
$= (2a)^2- (3)^2$
$= (2a + 3)(2a - 3)$ $\{\therefore a^2- b^2= (a + b)(a - b)\}$
$= (2a)^2- (3)^2$
$= (2a + 3)(2a - 3)$ $\{\therefore a^2- b^2= (a + b)(a - b)\}$
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