Question 1187054
f(t+h)=5t^2+10th+h^2
subtract 5t^2
get 10th +h^2
divide by  h
get 10t+h, and if t=3 that is 30+h net change.

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f(3)=45
f(3+h)=45+30h+h^2
subtract first from the second
get (30h+h^2)/h
=30+h