use recursion tree method for this type of problem. You'll get the answer easily.
like on first level $n^{2}$
/ \
$(n/4)^{2}$ $(n/2)^{2}$
/ \ / \
$(n/16)^{2}$ $(n/8)^{2}$ $(n/8)^{2}$ $(n/4)^{2}$
.......................................
............................ logn level
T(n) = $n^{2}{(1+\frac{5}{16}+(\frac{5}{16})^{2}............logn\, times)}$
T(n)= $n^{2}$(1) (it is decreasing GP so it will be close to 1.)
T(n) = $\Theta (n^{2})$