# How do you factor y= 7x^3+28x^2 ?

Dec 25, 2015

Both $7 {x}^{3}$ and $28 {x}^{2}$ are divisible by $7 {x}^{2}$, so:

$7 {x}^{3} + 28 {x}^{2} = 7 {x}^{2} \left(x + 4\right)$

#### Explanation:

$7 {x}^{3} = 7 {x}^{2} \cdot x$

$28 {x}^{2} = 7 {x}^{2} \cdot 4$

So:

$7 {x}^{3} + 28 {x}^{2} = \left(7 {x}^{2} \cdot x\right) + \left(7 {x}^{2} \cdot 4\right) = 7 {x}^{2} \cdot \left(x + 4\right)$