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X^(2)+x-20
splitting the middle term

1 Answer

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Are you trying to factorise this?

Here is a way you may not have been taught....
(x + a)(x + b) = x^2 + (a + b)x + ab

So you need to find two factors of -20 that add up to +1
-4 x 5 = -20 and -4 + 5 = 1. Perfect

x^2 + x - 20 = (x - 4)(x + 5)
User Fred The Fantastic
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