Answer
$2401 p^4 - 2744 p^3 q + 1176 p^2 q^2 - 224 p q^3 + 16 q^4$
Work Step by Step
$(x+y)^n=\binom{n}{0}x^ny^0+\binom{n}{1}x^{n-1}y^1+...+\binom{n}{a}x^{n-a}y^a+..\binom{n}{n}x^{0}y^n$
Here: $n=4$, $x=7p$, $y=-2q$
$(7p-2q)^4=\binom{4}{0}(7p)^{6}(-2q)^0+\binom{4}{1}(7p)^{4-1}(-2q)^1+\binom{4}{2}(7p)^{4-2}(-2q)^2+\binom{4}{3}(7p)^{4-3}(-2q)^3+\binom{4}{4}(7p)^{4-4}(-2q)^4=$
$2401 p^4 - 2744 p^3 q + 1176 p^2 q^2 - 224 p q^3 + 16 q^4$
