Check whether 7 + 3x is a factor of 3 x 3 + 7x.
Solution:

Let us divide $\left(3 x^{3}+7 x\right)$ by $(7+3 x)$. If the remainder obtained is 0 , then $7+3 x$ will be a factor of $3 x^{3}+7 x$.

By long division,

As the remainder is not zero, therefore, $7+3 x$ is not a factor of $3 x^{3}+7 x$.
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