# newbie differentation

• June 24th 2010, 06:45 AM
lukebushnell
newbie differentation
hi im a newbie to mathes and have been doing calculus recently ive. Been given two formulas and need to differentiate themthem and solve the equation, ive had a good attempt at them. i would just like to confirm if they are corret.

Attachment 17983
• June 24th 2010, 07:25 AM
Ackbeet
Your first one is incorrect, I think. Take the derivative first, without plugging in numbers. What do you get?

Your second one is confusing. I'm not sure what you mean on the LHS of the equals sign.
• June 24th 2010, 07:31 AM
Hello lukebushnell

The first one is:
$\dfrac{ds}{dt}= -15e^{-1.5t}$
When $t=0.7$
$\dfrac{ds}{dt}= -15e^{-1.05}$
$=-5.25$, correct to 3 s.f.

The second one is correct to 2 s.f. ( $2.21$ to 3 s.f.)