velocity problem!! be descriptive please

if a rock is thrown upward on the planet Mars with a velocity of 10 m/s, its height in meters t seconds later is given by y=10t-1.86t^{2}.

a.) find the average velocity for the given time intervals...

i.) (1,2)

ii.) (1,1.5)

iii.) (1, 1.1)

iv.) (1, 1.101)

v.) (1,1.001)

b.) find the instantaneous velocity when t=1.

please help and show steps to get your answer please!!!

Re: velocity problem!! be descriptive please

a)

i) At t= 1, what is the height? At t= 2, what is the height? What is the change in height during that 1 second? The average velocity is "change in height divided by change in time.

ii) At t= 1, what is the height? At t= 1.5, what is the height?

iii) At t= 1, what is the height? At t= 1.1, what is the height?

iv) At t= 1, what is the height? At t= 1.01 (I am sure it is NOT supposed to be "1.101") what is the height?

v) At t= 1, what is the height? At t= 1.001 what is the height?

vi) either make a "guess" at the limit, as the second t goes to 1 or take the derivative of the height function.