# Recent content by Dr Zoidburg

1. ### Question about graphing L(x,y) against f(x,y)

The question I'm stuck on is this: Let f(x,y) = (x+1)^2 + y^2 I'm asked to find the partial derivatives and then evaluate them at (1,2). From there, find L(x,y), the linear approximation to f(x,y) at (1,2). That part I'm ok with. I got the following: f_x(x,y) = 2(x+1) f_y(x,y) = 2y...
2. ### Testing for convergence/divergence

Thanks for the replies. It's helped me get my head around these problems better. I like jbunniii's solution. very clever and succinct. For this question: \lim_{n \to \infty} \frac {n^p}{a^n} = 0 my solution is: Apply L'Hopital's Rule: \frac{p}{ln(a)} [\lim_{n \to \infty} \frac...
3. ### Testing for convergence/divergence

I've got a couple of problems I'm stuck on. Any help gratefully received! Test for convergence/divergence: \sum_{n=1}^{\infty} \frac {(n+1)}{n^3 ln(n+2)} What test should I do here? Can I rearrange the equation to be: \frac{(\frac{1}{n^2} + \frac{1}{n^3})}{ln(n+2)} and then use...

15. ### Maximum area/volume problems

D'oh! I meant 12cm^{2} not 24. thanks for spotting that error. And thanks for the advice on Q2.