Tap the blue circles to see an explanation.
$$ \begin{aligned}15x(x+13x-7)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}15x(14x-7) \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}210x^2-105x\end{aligned} $$ | |
① | Combine like terms: $$ \color{blue}{x} + \color{blue}{13x} -7 = \color{blue}{14x} -7 $$ |
② | Multiply $ \color{blue}{15x} $ by $ \left( 14x-7\right) $ $$ \color{blue}{15x} \cdot \left( 14x-7\right) = 210x^2-105x $$ |