Question
Answer
$$(3b-4)(7b+1)=21b^2-25b-4$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(3b-4)(7b+1)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}21b^2+3b-28b-4 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}21b^2-25b-4\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{3b-4}\right) $ by each term in $ \left( 7b+1\right) $. $$ \left( \color{blue}{3b-4}\right) \cdot \left( 7b+1\right) = 21b^2+3b-28b-4 $$ |
| ② | Combine like terms: $$ 21b^2+ \color{blue}{3b} \color{blue}{-28b} -4 = 21b^2 \color{blue}{-25b} -4 $$ |
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