Answer
$16x^2+16x+4$
Work Step by Step
A binomial squared is equal to the square of the first term plus or minus twice the product of both terms plus the square of the second term.
$(a + b)^2= a^2 + 2ab + b^2$
$(4x+2)^2=(4x)^2+2(4x)(2)+2^2=16x^2+16x+4$