If you mean
3 sqrt(4x^2)*sqrt(6x^4)*3sqrt(9x),
thet equals
3*2x*sqrt6*x^2*9*sqrtx
= 54 sqrt6*x^(7/2)
3 radical 4x^2 time s radical 6x^4 times 3radical 9x
2 answers
I could not figure out what was intended.