# Math Help - Factor the Polynomial

1. ## Factor the Polynomial

Factor the polynomial: 64x^3 + 343

2. Originally Posted by magentarita
Factor the polynomial: 64x^3 + 343
Set it equal to zero and find the roots, that will give you a factor!

$64x^3+343 = 0$
$x = (\frac{-343}{64})^{\frac{1}{3}} = -\frac{7}{4}$

Hence $x +\frac{7}{4}$ is a factor.

Use long division to find $f(x)$ such that $(x+\frac{7}{4})f(x) = 64x^3+343$

You should get $(x+\frac{7}{4})(64x^2+112x+196) = 64x^3+343$

The quadratic in this equation is irreducible.

3. Originally Posted by magentarita
Factor the polynomial: 64x^3 + 343
You have (4x)^3 + 7^3. Now use the sum of cubes formula for factorising: Sum of Cubes

Note that the quadratic factor in this formula cannot be further factorised.

4. ## ok...

Originally Posted by mr fantastic
You have (4x)^3 + 7^3. Now use the sum of cubes formula for factorising: Sum of Cubes

Note that the quadratic factor in this formula cannot be further factorised.
I can take it from here.