The position of an object at time t is given by s(t) = -9 - 5t. Find the instantaneous velocity at t = 4 by finding the derivative.

Question

anonymous · Answer

please help!!!!

aum · Answer

s(t) = -9 - 5t
can you find ds/dt ?

anonymous · Answer

no im lost on this particular problem..im stuck :-(

aum · Answer

You have no calculus background?  You don't know the derivative of say, x^3, with respect to x?

anonymous · Answer

yes i do. but at this point, i'm basically going back and reviewing this stuff, i haven't looked at it in a while.

aum · Answer

What is the derivative of a constant?

anonymous · Answer

wait i think i have the answer

anonymous · Answer

is it -5

anonymous · Answer

-5t

anonymous · Answer

s'(t)= -5

aum · Answer

$$
s(t) = -9 - 5t \
s'(t) = -5 \
s'(4) = -5
$$

aum · Answer

The instantaneous velocity is s'(t) which is -5 and it is independent of time.  So the velocity remains the same at -5 no matter what the value of t.  Here they want instantaneous velocity at t = 4.  It is the same value of -5.

anonymous · Answer

thanks!!!have time for one more?

anonymous · Answer

Find an explicit rule for the nth term of the sequence.

3, -12, 48, -192, ...

@aum

aum · Answer

Do you see a common pattern in the numbers? 
What can you do to the first number to get the second number? 
Can the same thing be done to the second number to get the third number?
Can the same thing be done to the third number to get the fourth number?