Need help badly.. Average rate of change and slope of secant

[tkthustler]

y= f(x)= 4x^2 +10x:

Find the average rate of change in Y when X changes from 2 to 8.

I tried working it and got 63.33 so I guess I'm doing something wrong.

Next is find the slope of the secant line passing thru the points (1,f(1) and (1+h, f(1+H) ) Not sure if these two problems go together but I'm clueless if anyone could help me out I would be most appreciative. Thx so much

-Brian

 

[skeeter]

first part.

average rate of change = [f(8) - f(2)]/(8 - 2) = 300/6 = 50


second part

average rate of change = [f(1+h) - f(1)]/[(1+h) - 1]
where ...
f(1+h) = 4(1+h)² + 10(1+h)
f(1) = 14

 

[tkthustler]

Thanks skeeter I owe you big time!