2、v=[s(t0+ 1)-s(t0)]/(t0+ 1-t0)=[(5t0^2+ 10t0+5)-5t0^2]/ 1= 10t0+5

3.v=[S(T0+ triangle T)-S(T0)]/(T0+ triangle T-T0)=( 10T0* triangle T+5 triangle T 2)/ triangle T= 10T0+5 triangle T.

4 、[ 1.2， 1.20 1]v = 12.005

v= 12