How do you factor: $y= x^3 + x^2 − 20x$ ?

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Answer 1 · 2015-12-02T15:01:33

Factor $y = x^3 + x^2 - 20x$

$y = xY = x(x^2 + x - 20)$ . Factor $Y$

Find 2 numbers knowing sum (1) and product (-20).
Factor pairs of $-20 -> (-2, 10)(-4, 5)$ . This sum is $-4 + 5 = 1 = b$ .

Therefore, the 2 numbers are $-4$ and $5$ .

Factored form:

$y = xY = x(x - 4)(x + 5)$

How do you factor: y= x^3 + x^2 − 20x y= x^3 + x^2 − 20x ?