Question

Suppose f(t)=(3t^3)+(5t^2)+3t-5
Find the value of t n the interval [4,8] where f(t) takes on its minimum.

Answer 1

find the first derivative, set it equal to 0:
f'(t) = 9t^2 + 10t + 3

Answer 2

9t^2 + 10t + 3 = 0
solve for t

Answer 3

quadratic formula?

Answer 4

yea

Answer 5

ok i get -10+-sqrt(-8) / 18

Answer 6

so?

Answer 7

@saifoo.khan

Answer 8

@mariomintchev

Answer 9

Yes. u are correct

Answer 10

lol

Answer 11

what else do i do to get the final answer? thats not the final answer

Answer 12

Now insert that value in the original equation to get the value of "y"

Answer 13

how would i plug in the answer i got into it? its all weird because theres no square root of 8.

Answer 14

?

Answer 15

Oh since u got imaginary roots, just check the endpoints. Plug in 4 into f(t) and 8 into f(t)
whichever's smaller is ur min.