Question
Factorise:
$x^2-9 x+20$
$x^2-9 x+20$
✓
Answer
$x^2-9 x+20$
$=x^2-5 x-4 x+20$
$\{20 = (-5) × (-4), -9 = -5 - 4\}$
$= x(x - 5) - 4(x - 5)$
$ = (x - 5)(x - 4)$
$=x^2-5 x-4 x+20$
$\{20 = (-5) × (-4), -9 = -5 - 4\}$
$= x(x - 5) - 4(x - 5)$
$ = (x - 5)(x - 4)$
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