Factorise: 20 x^2-45 - Vidyadip

Question

Factorise:
$20 x^2-45$

✓

Answer

$20 x^2-45$
$=5\left(4 x^2-9\right)$
$=5\left[(2 x)^2-(3)^2\right]$
$=2(1+5 x)(1-5 x)\left[\therefore a^2-b^2=(a-b)(a+b)\right]$
$=5(2 x+3)(2 x-3)$

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