Question

x²-4x-21 factorisation
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Answer 1

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• Factorise ${x}^{2} - 4x - 21$

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

$= {x}^{2} - 7x + 3x - 21$

$= x(x - 7) + 3(x - 7)$

$= (x + 3)(x - 7)$

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• $(x + 3)(x - 7)$

Answer 2

Answer:

to do factorization multiply coefficiant of x^2 and

constant term

-21*1=-21

express the prouct as sum of two numbers whose sum is coeficiant of x

-21= -7*3

now replace x term by it

x²-4x-21

x²-7x+3x-21

take common terms out

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

now take (x-7) common

(x-7)(x+3)

this is the procedure we follow while factorizing a quadratic polynomial

hope this helps u

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