[10] 4. Use implicit differentiation on these. a) Find an expression for dy/dr at any point on the curve cos(y?) + er+2y = 8. b) For the curve 12 - Ary = y' + 9, do the following: (i) Show that the point (-1, 2) is on the curve. (ii) Find an equation for the line that's tangent to the curve at (-1, 2)