I don't understand how to do this, so please help. Could you show the steps , so I can try it own my ow to see if I can get it.Thank you.

2SQRT4t^9z^2.

start here:

2*sqrt(4t^9 z^2)=
2sqrt(4)*sqrt(t^9)*sqrt(z^2)

note on the second term, sqrt(t^9)=sqrt(t^8)sqrt(t)