# Thread: Help with test study

1. ## Help with test study

I have a calc test coming up and I need help in the following areas. If you can help it would be great.

I need help with implicit differentiation. For instance differentiaite xy+8x=10-2y. I'm really stuck in this area. Obviously differentiating 8x is 8, 10 is 0 and -2y is -2 but the xy part has me confused.

How do I simplify (1+3i)(3+2i). I thought you just times it out but that's not the answer.

Also using the Newton Raphson process to determine a value of x for which f(x)=0 using x1=1 and giving answer to five decimal places. f(x)=x^2+7x-3

Finally differentiating cos^(0.5)x, sqrt (sin x), f(x)=x cos x, f(x)=x^2 cos x and f(x)=(sin x)/x.

I understand that's quite a bit but they are the areas I'm struggling in.

2. Originally Posted by Mickey
I have a calc test coming up and I need help in the following areas. If you can help it would be great.

I need help with implicit differentiation. For instance differentiaite xy+8x=10-2y. I'm really stuck in this area. Obviously differentiating 8x is 8, 10 is 0

and -2y is -2 Mr F says: No. It's $\displaystyle {\color{red} -2 \frac{dy}{dx}}$. This I think reveals why you have this trouble - you do not appreciate that y is a function of x.

but the xy part has me confused. Mr F says: Use the product rule to get $\displaystyle {\color{red}y + x \frac{dy}{dx}}$.

How do I simplify (1+3i)(3+2i). I thought you just times it out but that's not the answer. Mr F says: You do. Obviously you've made a careless error. Post >all< your working and I will point out the errror(s).

Also using the Newton Raphson process to determine a value of x for which f(x)=0 using x1=1 and giving answer to five decimal places. f(x)=x^2+7x-3 Mr F says: Apply the procedure in the usual way.

Finally differentiating cos^(0.5)x, sqrt (sin x), f(x)=x cos x, f(x)=x^2 cos x and f(x)=(sin x)/x. Mr F says: Use chain rule, chain rule, product rule, product rule and quotient rule. Follow the examples you ought to have in your class notes or text book Alternatively, you will find dozens of similar questions with solutions posted in this forum.

I understand that's quite a bit but they are the areas I'm struggling in.
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