Factorize each of the following algebraic expressions:
In order to factorize the given expression, we find to find two numbers p and q such that:
p + q = -4, pq = -21
Clearly,
3 – 7 = -4, 3 (-7) = -21
Therefore, split (-4x) as 3x – 7x
Therefore,
x2 + 4x – 21 = x2 + 3x – 7x – 21
= x (x + 3) – 7 (x + 3)
= (x – 7) (x + 3)
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