sqrt(4x^2 + 9x^4) = sqrt(x^2*(4+9x^2)) = |x|*sqrt(4+9x^2)) is that absolute value sign always necessary when you take out an x squared from under the radical? what if it is something like
sqrt(4*t^2*sin^2(t^2)+4*t^2*cos^2(t^2)))
does that turn out to be |2t|*sqrt(sin^2(t^2)+cos^2(t^2))