Question

determine the value of a so that the average rate of change of the function j(x)= 3x²+ax-4 over the interval -1≤x≤2 is 8

Answer 1

average rate of change, as in \(\frac{f(2)-f(-1)}{3}=8\) ?

Answer 2

we can do this for sure

Answer 3

you want \[\frac{f(2)-f(-1)}{3}=8\] or
\[f(2)-f(-1)=24\] so lets compute the left hand side okay?

Answer 4

\[f(2)=12+2a-4=2a+8\] and
\[f(-1)=3-a-4=-a-1\] you with me so far?

Answer 5

yep

Answer 6

so you want
\[2a+8-(-a-1)=24\] i.e.
\[3a+9=24\]

Answer 7

oh! and then solve for a

Answer 8

yeah should take only two steps right?

Answer 9

3a=24-9
3a=15
a=5

Answer 10

YAY! awesome thanks ! :)

Answer 11

that ought to do it, yes

Answer 12

yw