Answer
$\left( 10x+17\right) ^{2}$
Work Step by Step
$4\left( 5x+7\right) ^{2}+12\left( 5x+7\right) +9=\left( 2\left( 5x+7\right) \right) ^{2}+2\times \left( 2\left( 5x+7\right) \right) \times 3+3^{2}=\left( 2\left( 5x+7\right) +3\right) ^{2}=\left( 10x+17\right) ^{2}$
