What is the factored form of the following expression?
x2 – x – 42
a. (x – 7)(x + 6)
b. (x + 7)(x + 6)
c. (x + 7)(x – 6)
d. (x – 7)(x – 6)

M? aoc=96 ? space, m, angle, a, o, c, equals, 96, degree \qquad m \angle boc = 8x - 67^\circm? boc=8x? 67 ? space, m, angle, b, o, c, equals, 8, x, minus, 67, degree \qquad m \angle aob = 9x - 75^\circm? aob=9x? 75 ? space, m, angle, a, o, b, equals, 9, x, minus, 75, degree find m\angle bocm? bocm, angle, b, o, c: