how to solve quadratic equations by graphical method?
['Use the graph of y = x2 + x - 6 to solve x2 + x - 6 = 0.', 'Use the graph of y = -x2 + 4 to solve -x2 + 4 = 0.', 'Use the graph of y = x2 -2x + 1 to solve x2 -2x + 1.', 'Use the graph of y = x2 + 1 to solve x2 + 1.']