Question

the displacement of a particle from a point O is s meters at time t seconds after some initial time where s =2t^3 -7t^2+4t+5
what is the greatest velocity in the negative direction?

Answer 1

s =2t^3 -7t^2+4t+5
s'=6t^2-14t+4 :velocity
s''=12t-14
0=12t-14
t=14/12 :time for greatest velocity

s'=6(14/12)^2-14(14/12)+4
s'= -4.167

Answer 2

how come in the solution book it says the answer is 4.25cm/s?

Answer 3

why is it 4.25.... @.@
but i think i should be 4.167 since it is asking for -s'