1. (a) 0 = x² + 4x - 12 (Switch Sides)
x² + 4x - 12 = 0 (Factor Expression)
(x - 2)(x + 6) = 0 (Apply the Zero Factor Principle)
x = 2, and x = - 6
x - intercept : (2, 0) and ( - 6, 0)
(b) y = (0)² + 4(0) - 12 (Simplify)
y = 0 + 4 * 0 - 12 = 0 + 0 - 12 = - 12
y - intercept : (0, - 12)
(c) Our vertex belongs to an upward facing parabola, and hence it will be a minimum, of ( - 2, - 16).
2. Seth's solution is not accurate. He did the calculations accurately, and ended up with x = 3 and x = - 2. However he forgot to substitute those values back into the equations y = x² + 3x - 5 and y = 4x + 1, solving for the y values. Instead of being ( - 2, 0) and (3, 0) it should have been (3, 13), ( - 2, - 7)...
y = (3)² + 3(3) - 5 = 9 + 9 - 5 = 18 - 5 = 13,
y = 4( - 2) + 1 = - 8 + 1 = - 7
Hence we get the solutions (3, 13) and ( - 2, - 7).