derivative of t^5/2*(7-t)?

Question

i believe my caculus text is giving me the wrong answer
can anyone help
thank you !

Answer 1

f (t) = 7t^(5/2) - t^(7/2)
f `(t) = (35/2) t^(3/2) - (7/2) t (5/2)
f `(t) = (7/2)t^(3/2) [ 5 - t ]