Find roots of polynomial $$ p(x) = 15x^2+120x $$

The roots of polynomial $ p(x) $ are:

$$ \begin{aligned}x_1 &= 0\\[1 em]x_2 &= -8 \end{aligned} $$

Step 1:

Factor out $ \color{blue}{ 15x }$ from $ 15x^2+120x $ and solve two separate equations:

$$ \begin{aligned} 15x^2+120x & = 0\\[1 em] \color{blue}{ 15x }\cdot ( x+8 ) & = 0 \\[1 em] \color{blue}{ 15x = 0} ~~ \text{or} ~~ x+8 & = 0 \end{aligned} $$

One solution is $ \color{blue}{ x = 0 } $. Use second equation to find the remaining roots.

Step 2:

To find the second zero, solve equation $ x+8 = 0 $

$$ \begin{aligned} x+8 & = 0 \\[1 em] x & = -8 \end{aligned} $$

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