If y = (x^2 + 3x)cosx , find the value of dy/dx when x=0

Can someone show me how to do this q please.

Thanks

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- Sep 12th 2010, 08:06 AMDetanonQuotient rule question.
If y = (x^2 + 3x)cosx , find the value of dy/dx when x=0

Can someone show me how to do this q please.

Thanks - Sep 12th 2010, 08:20 AMe^(i*pi)
Quotient Rule? You'd be much better off with the Product Rule since we're not doing any division here.

The product rule is $\displaystyle \dfrac{dy}{dx} \left[u(x)v(x)\right] = v\dfrac{du}{dx} + u\dfrac{dv}{dx}$

In your case $\displaystyle u = x^2 +3x$ and $\displaystyle v = \cos(x)$

Once you've differentiated find $\displaystyle y'(0)$. For reference I get an answer of 3