#### Answer

$(3p-7)^{2}$

#### Work Step by Step

Given the polynomial
$(3p)^{2}$ - 42p + $(7)^{2}$
We see that the polynomial has the first and last term squared and the middle term is -2 times the first and last term. Thus it follows the rule of
$a^{2}$ - 2ab + $b^{2}$ = $(a-b)^{2}$
In this polynomial a= 3p and b=7
$(3p)^{2} - 2(3p)(7) + (7)^{2} =(3p-7)^{2}$