Answer
$(3x+2)^2 \ne 9x^2+4$ because the square of $3x+2$ is $9x^2+12x+4$.
Work Step by Step
RECALL:
$(a+b)^2=a^2 + 2ab+b^2$
$(3x+2)^2$ does not equal $9x^2+4$ because the square of a binomial is a trinomial.
Squaring the binomial gives:
$(3x+2)^2
\\=(3x)^2+2(3x)(2)+2^2
\\=9x^2+12x+4$
