Square root of 3x^2y^3 times 2 square root of 72x^3y^4

Which of the following is most likely the next step in the series? a3z, b6y, c9x, d12w, е15v, f18u

The following division is being performed using multiplication by the reciprocal find the missing numbers is 5/12 divided by x/3 equals 5/12 times x/10 equals 1/x

Look at this pattern ; 1,4,9, number 10000 belongs in this pattern . what’s the place of this number?