Question

How do you factor `21x^3 - 28x`?

Answer 1

`x = 0 or x = +-(2sqrt3)/3`

Explanation:

Start by taking out the common factor, 7x
`7x(3x^2 - 4) = 0`
`7x = 0 or 3x^2 - 4 = 0`
`x = 0 or x^2 = 4/3`
`x = 0 or x = +-2/sqrt3`

`x = 0 or x = +-(2sqrt3)/3`