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Alg2 lesson 7-5
- 4. Write a polynomial function of least degree with
integer coefficients whose zeros include 2, 1 and -3
x=2 x=1 x = -3
x–2=0 x–1=0 x+3=0
(x – 2)(x – 1)(x + 3) = 0
(x2 – 3x + 2)(x + 3) = 0
x3 + 3x2 – 3x2 – 9x + 2x + 6 = 0
x3 – 7x + 6 = 0
- 5. Write a polynomial function of least degree with
integer coefficients whose zeros include 4 and 4 – i.
Complex
x=4 x=4–i x=4+i zeros occur
in
x–4=0 x–4+i=0 x–4–i=0 conjugate
pairs
(x – 4) (x – 4 + i) (x – 4 – i)
+1
x2 – 4x – xi – 4x + 16 + 4i + xi – 4i – i2
(x – 4) x2 – 8x + 17
- 7. State the possible number of positive real zeros, negative
real zeros, and imaginary zeros of
2 sign changes
+ + +
2 or 0 positive zeros
f(-x) = (-x)3 – (-x)2 + 2(-x) + 4
1 sign change
= x3 – x2 – 2x + 4 1 negative zero
+
2 or 0 imaginary zeros.
- 8. State the possible number of positive real
zeros, negative real zeros, and imaginary zeros of
2 sign changes
+ + + +
2 or 0 positive zeros
p(-x) = (-x)4 – (-x)3 + (-x)2 + (-x) + 3
2 sign changes
= x4 + x3 + x2 - x + 3
2 or 0 negative zeros
+ + + +
4, 2, or 0 imaginary zeros.