Mathematics
Factorise the following:
x2 - 6xy - 7y2
Factorisation
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Answer
To factorise x2 - 6xy - 7y2, 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 - 6xy - 7y2 = x2 - 7xy + xy - 7y2
= x(x - 7y) + y(x - 7y)
= (x - 7y)(x + y).
Hence, x2 - 6xy - 7y2 = (x - 7y)(x + y).
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