vertex of the parabola given by y = -4 . . (c) This part of the question concerns the quadratic function y = x + 18x + 42. (i) Write the quadratic expression x+ 18x + 42 in completed-square form. [2] (ii) Use the completed-square form from part (c) (i) to solve the equation x2 + 18x + 42 = 0, leaving your answer in exact (surd) form. [3] (iii) Use the completed-square form from part (c) (i) to write down the coordinates of the vertex of the parabola y = x2 + 18x + 42. [1] (iv) Provide a sketch of the graph of the parabola y = x4+ 18x + 42, either by hand or by using a suitable graphing software package like Graphplotter. [3] If you intend to go on to study more mathematics, then you are advised to sketch the graph by hand for the practice. Whichever method you choose, you should refer to the graph-sketching strategy box in Subsection 2.4 of Unit 10 for information on how to sketch and label a graph correctly