# How do you multiply (2x+5)^3?

Apr 7, 2015

If there is $\left(a + b\right) \left(c + d\right)$ then:

$\left(a + b\right) \left(c + d\right) = a \cdot c + a \cdot d + b \cdot c + b \cdot d$

${\left(2 x + 5\right)}^{3} = \left(2 x + 5\right) \cdot \left(2 x + 5\right) \cdot \left(2 x + 5\right)$

$= \left[4 {x}^{2} + 10 x + 10 x + 25\right] \cdot \left(2 x + 5\right)$

If there is $\left(a + b + c\right) \left(d + e\right)$ then:

$\left(a + b + c\right) \left(d + e\right) = a d + a e + b d + b e + c d + c e$

$= \left(4 {x}^{2} + 20 x + 25\right) \cdot \left(2 x + 5\right)$

$= 8 {x}^{3} + 20 {x}^{2} + 40 {x}^{2} + 100 x + 50 x + 125$

$= 8 {x}^{3} + 60 {x}^{2} + 150 x + 15$