Q4 on 2017 Edexcel C4 paper, concerns differentiation of multiple variables.

(a) Asks to differentiate an equation C: 4x² - y³ - 4xy + 2^y = 0Then use the fact that point P (-2,4), lies on C to find an expression for dy/dx Differential of form 8x - 3y²(dy/dx) - (4y + 4x(dy/dx)) + 2^yln2(dy/dx) = 0Rearrange and substitute to find dy/dx(b) Asks to find the point where the Normal to C at P intersects the y axis. (form of p + qln2)-1/(dy/dx) to find gradient of normal to C at P, then use x = 0 at Y axis intercept to find y coordinate.