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## Homework Statement

Determine the acceleration after 6 seconds.

## Homework Equations

s(t) = sqrt12t - 8 where s is in metres and t is in seconds.

## The Attempt at a Solution

v=s'(t)=6/sqrt12t-8

this is where i don't understand...they got a positive value for 36 in the book and i got a negative value...here is my work below that got me to a negative value...what did i do wrong?

a=v'(t)=0*sqrt12t-8 - 6/sqrt12t-8*6/(sqrt12t-8)^2

= - 36/sqrt12t-8/(sqrt12t-8)^2

= - 36/(12t-8)^3