Question

Let s(t) = 9t^2 + 2t + 70 be the position, in miles, of a car driving on a straight road at time t, in hours. The car's velocity at any time t is given by v(t) = 18t + 2. Find the car's position when the car is going 74 mph.

Answer 1

so let v(t) = 74 and solve for t

when you get t, substitute it into the position equation.

Answer 2

ok. let me try

Answer 3

so i got the answer as 16018742

Answer 4

do i leave it like that?

Answer 5

well start with v(t)

74 = 18t + 2

can you solve for t...?

Answer 6

its 4

Answer 7

222

Answer 8

thats correct now subsitute it into position

\[s(4) = 9\times(4)^2 + 2\times 9 + 70\]

Answer 9

that's correct...

the car is 222 miles to the right of its starting point

Answer 10

ok

Answer 11

ooops middle term should be 2 x 4... sorry about that not 2 x 9

Answer 12

ok

Answer 13

thanks