d(f(x)/dx
=d(3x^4 *(x-1)^1/2)/dx
=(x-1)^(1/2)*d(3x^4)/dx + 3x^4*d((x-1)^(1/2))/dx
=12*(x-1)^(1/2)*x^3+3/2*x^4*(x-1)^(-1/2)