PreCalculus
Find all of the real zeros of the function. Give exact values whenever possible. Identify each zero as rational or
irrational.
11) f(x) = x 3 - 2x 2 - 6x + 12
A) 2 (rational), 2 6 (irrational), and -2 6 (irrational)
B) -2 (rational), 6 (irrational), and - 6 (irrational)
C) 2 (rational), 6 (irrational), and - 6 (irrational)
D) 2 (rational), 6 (rational), and -6 (rational)
12) f(x) = x 3 - 7x 2 + 4x + 30
A) 5 (rational), 2 + 7 (irrational), and 2 - 7 (irrational)
B) 5 (rational), 7 (irrational), and - 7 (irrational)
C) 5 (rational), 8 (rational), -6 (rational)
D) 5 (rational), 1 + 7 (irrational), and 1 - 7 (irrational)
13) f(x) = x 3 - 7x 2 + 10x + 6
A) 3 (rational), 2 + 6 (irrational), and 2 - 6 (irrational)
B) 3 (rational), 6 (irrational), and - 6 (irrational)
C) 3 (rational), 1 + 6 (irrational), and 1 - 6 (irrational)
D) 3 (rational), -2 + 6 (irrational), and -2 - 6 (irrational)
Write the polynomial in standard form and identify the zeros of the function.
14) f(x) = (x - 5i)(x +5i)
A) f(x) = x 2 - 25; zeros ± 5i
B) f(x) = x 2 + 5ix + 25; zeros ± 5
C) f(x) = x 2 + 25; zeros ± 5
D) f(x) = x 2 + 25; zeros ± 5i
15) f(x) = (x - 1)(x - 7i)(x + 7i)
A) f(x) = x 3 - x 2 + 49x - 49; zeros 1, ± 7i
B) f(x) = x 3 - x 2 + 7x - 7; zeros 1, ± 7i
C) f(x) = x 3 - x 2 - 7x + 7; zeros 1, ± 7i
D) f(x) = x 3 - x 2 - 7x + 7; zeros -1, ± 7i
16) f(x) = (x + 2)(x + 2)(x + 3i)(x - 3i)
A) f(x) = x 4 + 4x 3 + 13x 2 + 36x + 36; zeros 2 (mult. 2), ± 3i
B) f(x) = x 4 + 4x 3 - 5x 2 - 36x - 36; zeros -2 (mult. 2), ± 3
C) f(x) = x 4 + 4x 3 + 13x 2 + 36x + 36; zeros -2 (mult. 2), ± 3i
D) f(x) = x 4 + 13x 2 + 36; zeros 2 (mult. 2), ± 3
Write a polynomial function of minimum degree with real coefficients whose zeros include those listed. Write the
polynomial in standard form.
17) 4i and 3
A) f(x) = x 4 - 13x 2 - 48
B) f(x) = x 4 - 26x 2 + 48
C) f(x) = x 4 + 26x 2 + 48
D) f(x) = x 4 + 13x 2 - 48
18) 7, -11, and 2 + 8i
A) f(x) = x 4 - 145x 2 + 580x - 5236
B) f(x) = x 4 - 25x 2 + 580x - 5236
C) f(x) = x 4 - 9x 3 - 56x 2 + 290x - 5236
D) f(x) = x 4 - 9x 3 + 56x 2 - 290x + 5236
Calin M. Agut - 2012