Mathematics
Factorise the following:
x2 + 6x - 7
Factorisation
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Answer
To factorise x2 + 6x - 7, we want to find two real numbers whose sum is 6 and product is -7. By trial, we see that 7 - 1 = 6 and 7 × -1 = -7.
∴ x2 + 6x - 7 = x2 + 7x + (-1x) - 7
= x2 + 7x - x - 7
= x(x + 7) - 1(x + 7)
= (x - 1)(x + 7).
Hence, x2 + 6x - 7 = (x - 1)(x + 7).
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