7 (a) The table shows some values for y = 4x . (i) Complete the table. (ii) Draw the graph of y = 4^x for 0 =< x =< 3. (iii) By drawing a tangent, estimate the gradient of the curve when x = 2. (iv) The solutions of the equation 3(4^x) +ax+b = 0 can be found from the points of intersection of y = 4^x and y = 20x-12. (a) Find the value of a and the value of b. (b) By drawing the line y = 20x-12 on the grid opposite, find all the solutions of 3(4^x) +ax+b = 0 . (b) Here is a sketch of the graph of a quadratic function. The curve has a maximum point (p, q). Find the value of p and the value of q.