Question

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

Answer 1

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

Explanation:

`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)`