The expression is factorable. Because the center term is negative, you have a positive root and a negative root that differ by 2. Ask yourself, What 2 numbers differ by two and yield 24 (4 and 6). Because the sum of the factors must yield -2, you know 6 is negative:
(x+4)(x-6) = f(x) You know that it is an upward concave quadratic with 0's (crossing axis) at x = -4 and 6. You know that the vertical axis of the parabola is at x = (-4+6)/2 = 1 and the vertex point is at (1, -25) from plugging into either from of the equation.
