Mathematics
One of the factors of (x2 - 4x)(x2 - 4x - 1) - 20 is :
x - 1
x - 2
x - 4
x + 5
Factorisation
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Answer
Given,
(x2 - 4x)(x2 - 4x - 1) - 20
Let us consider y = (x2 - 4x)
⇒ (y)(y - 1) - 20
⇒ y2 - y - 20
⇒ y2 - 5y + 4y - 20
⇒ y(y - 5) + 4(y - 5)
⇒ (y + 4)(y - 5)
⇒ (x2 - 4x + 4)(x2 - 4x - 5)
⇒ [(x)2 - 2(2)(x) + (2)2](x2 - 5x + x - 5)
⇒ (x - 2)2[x(x - 5) + 1(x - 5)]
⇒ (x - 2)(x - 2)(x + 1)(x - 5)
Hence, option 2 is correct option.
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