#### Answer

$(7x+5)(2x+3)$.

#### Work Step by Step

The given polynomial is
$=14x^2+31x+15$
Rewrite $31x$ as $10x+21x$.
$=14x^2+10x+21x+15$
Group the terms.
$=(14x^2+10x)+(21x+15)$
Factor each group.
$=2x(7x+5)+3(7x+5)$
Factor out $(7x+5)$.
$=(7x+5)(2x+3)$
Hence, the factor of the polynomial is $(7x+5)(2x+3)$.