to get the equation of a line, we simply need two points, say for the Red one ... notice in the graph the lines passes through (0,2) and (-1,6), so let's use those
now, for the Blue one, say let's use hmmm it passes through (0,2) and (1.6)
When c = -3,
-3c² + c - 2c = -3c² - c
= -3(-3)² - (-3)
= -24