SOLUTION
In this question, we need to factor the polynomial.
[tex]\begin{gathered} 21x^3+6x^2\text{ - 28 x - 8} \\ \end{gathered}[/tex]Factoring:
[tex]21x^3+6^{}x^2\text{ - 28 x 8}[/tex]First, we split the expression at hand into groups, each group having two terms :
[tex]\begin{gathered} \text{Group 1 : -28 x - 8} \\ \text{Group 2 : 21 x}^3+6x^2 \end{gathered}[/tex]Pull out from each group separately :
Group 1: (7x+2) • (-4)
Group 2: (7x+2) • (3x^2)
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Add up the two groups :
[tex](7x+2)(3x^2\text{ - 4 )}[/tex]Which is the desired factorization
