Answer:
f(-3) = p(-3)³ - 3q + r = -12
f(2) = p(2³)+ 2q + r = -12
f(-1) = p(-1)³ - q + r = 0
-27p - 3q + r = -12
8p + 2q + r = -12
-p - q + r = 0
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p = 1, q = -7, r = -6
f(x) = x³ - 7x - 6 = (x + 2)(x + 1)(x - 3)
The zeroes of f(x) are -2, -1, and 3.