Tap the blue circles to see an explanation.
| $$ \begin{aligned}(5z-4)(5z-7)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}25z^2-35z-20z+28 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}25z^2-55z+28\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{5z-4}\right) $ by each term in $ \left( 5z-7\right) $. $$ \left( \color{blue}{5z-4}\right) \cdot \left( 5z-7\right) = 25z^2-35z-20z+28 $$ |
| ② | Combine like terms: $$ 25z^2 \color{blue}{-35z} \color{blue}{-20z} +28 = 25z^2 \color{blue}{-55z} +28 $$ |