Answer
$8x^3+12x^2+6x+1$
Work Step by Step
Apply Binomial Theorem.
$(a+b)^n=\sum_{r=0}^n\dbinom{n}{r}(a)^{n-r}b^r$
$(2x+1)^3=\dbinom{3}{0}(2x)^3(1)^0+\dbinom{3}{1}(2x)^2(1)^1+\dbinom{3}{2}(2x)^1(1)^2+\dbinom{3}{3}(2x)^0(1)^3$
or, $=8x^3+(3)(4x^2)+6x+1$
or, $=8x^3+12x^2+6x+1$
