Question 91 (v)

Factorise the following:

$y^{2} + 4 y - 21$

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Solution

We have, $y^{2} + 4 y - 21$
$= y^{2} + (7 - 3) y - 21 = y^{2} + 7 y - 3 y - 21 = y (y + 7) - 3 (y + 7) = (y + 7) (y - 3)$

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Question 91 (iii)

Factorise the following:

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4 x^{2} + 4 x + 1

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