Answer
$(8x+7)^{2}$
Work Step by Step
$64x^{2}+112x+49=$
...write first and last terms as squares.
$=(8x)^{2}+112x+(7)^{2}$
...does middle term equal $2ab$?
$112x=2\cdot(8x)\cdot(7)$
$=(8x)^{2}+2\cdot(8x)\cdot(7)+(7)^{2}$
...write as the square of a binomial.
$=(8x+7)^{2}$
