# newbie differentation

#### lukebushnell

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.

#### Ackbeet

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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.

MHF Hall of Honor
Hello lukebushnell

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

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