Differentiation structured questions

Hey,

I need help with some questions that I have been stuck with on my crash course to teach myself calculus before school starts.

1) If , show that

I have tried to solve for the derivatives of y and I derived extremely complicated fractions with powers of 3/2 and such and I cannot simplify the equation to = 0.

2)

a) (found)

b) Using your answer in (a) , differentiate the following with respect to x

For this, I am unsure of what to let be u so that I can use the chain rule in the form

or

I have dealt with trigo functions like sin^8(x) and sin(8x) but never in the form that the question gave (8th power only applies to the fraction and not the whole function) and I do not know how to proceed.

Any help at all is appreciated :)