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y=(4x^2+1)^5                        y=u^5          u=4x^2+1

                                             y’=5u^4   (wrt u)  u’=8x

y’=40x(4x^2+1)^4

y’=40x(4x^2+1)^4=0             x=0  ...

Each part can be done separately, so x^2 becomes 2x, xy becomes dy/dx + y by product rule, y^2 becomes 2y(dy/dx) by chain rule, and 1 becomes 0. Hence the answer is 2x + y + (2y+1)dy/dx = 0, but the answe...

x^2=y+1 therefore 6y+2y+2=6 therefore 8y=4 y=0.5 sub in to either equation x=(3/2)^0.5

To differentiate we multiply by the power and take one off the power. d/dx(3x^2+1/x)= 6x-1/x^2 At a stationary point the gradient equals zero 6x-1/x^2=0 which rearranges to x=(1/6)^(1/3)

Firstly look for key terms in the question, identifying that we are going to be finding the sum of n terms, and it is an arithmetic series. This allows us to know which e...