Factorise x squared + 7x minus 120

asked Dec 13, 2021 40.0k views

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Answer:

$\huge\boxed{x^2+7x-120=(x+15)(x-8)}$

Explanation:

$x^2+7x-120\\\\\left\{\begin{array}{ccc}a+b=7\\ab=-120\end{array}\right\Rightarrow a=15,\ b=-8$

$x^2+7x-120=x^2+15x-8x-120=x(x+15)-8(x+15)\\\\x^2+7x-120=(x+15)(x-8)$

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