Question

Factorise (x2−4x) (x2-4x-1-20) please answer

Answer 1

Answer:

x (x-4) (x-3) (x+7)

Step-by-step explanation:

(X²-4x) (x²-4x-1-20)

(X²-4x) (x²-4x-21)

x(x-4) (x²-3x+4x-21)

X(x-4) (x(x-3)+7(x-3))

x (x-4) (x-3) (x+7)

Answer 2

Answer:

Step-by-step explanation:

$(x^{2} - 4x) (x^{2} - 4x - 1 - 20)$

$(x^{2} - 4x) (x^{2} - 4x - 21)$

$(x^{2} - 4x) (x^{2} + 3x - 7x - 21)\\\\= (x^{2} - 4x) [x ( x + 3 ) - 7( x + 3 )]\\\\= (x^{2} - 4x)(x - 7)( x + 3 )\\\\= [x^{2} - (2\sqrt{x})^{2} ] (x - 7)( x + 3 )$

using $a^{2} - b^{2}$ = (a + b)(a - b)

$=(x + 2\sqrt{x}) (x - 2\sqrt{x}) (x - 7) (x + 3)$