Math Problem Statement

Show that the given values of c are zeros of P(x). P(x) = 2x4 − x3 − 14x2 − 5x + 6, c = −2, 1 2 To show that c = −2 is a zero of P(x), we first evaluate P(x) at x = −2. P(x) = 2x4 − x3 − 14x2 − 5x + 6 P(−2) = 2

0

4

− (−2)3 − 14(−2)2 − 5(−2) + 6 = 2

− (−8) − 14(4) − 5(−2) + 6

We have shown that P(−2)

. By the Factor Theorem, this means that x + 2 ---Select--- a factor of P(x), so −2 is a zero of P(x). To show that c = 1 2 is a zero of P(x), we first evaluate P(x) at x = 1 2 . P(x) = 2x4 − x3 − 14x2 − 5x + 6 P 

1 2

= 2

4

1 2 3

− 14

1 2 2

− 5

1 2

  • 6 = 2

1 8

− 14

1 4

− 5

1 2

  • 6 = We have shown that P 

1 2

= . By the Factor Theorem, this means that x − 1 2

---Select--- a factor of P(x), so 1 2 is a zero of P(x). Find all other zeros of P(x). (Enter your answers as a comma-separated list. Enter all answers using the appropriate multiplicities.) x =

Solution

To show that c=2c = -2 and c=12c = \frac{1}{2} are zeros of P(x)=2x4x314x25x+6P(x) = 2x^4 - x^3 - 14x^2 - 5x + 6, we will evaluate P(x)P(x) at x=2x = -2 and x=12x = \frac{1}{2} step by step, and then use the Factor Theorem. Afterward, we will find the remaining zeros.

Step 1: Check if c=2c = -2 is a zero of P(x)P(x).

We need to evaluate P(2)P(-2):

P(x)=2x4x314x25x+6P(x) = 2x^4 - x^3 - 14x^2 - 5x + 6

P(2)=2(2)4(2)314(2)25(2)+6P(-2) = 2(-2)^4 - (-2)^3 - 14(-2)^2 - 5(-2) + 6

Calculating each term:

(2)4=16,(2)3=8,(2)2=4(-2)^4 = 16, \quad (-2)^3 = -8, \quad (-2)^2 = 4

P(2)=2(16)(8)14(4)5(2)+6P(-2) = 2(16) - (-8) - 14(4) - 5(-2) + 6 P(2)=32+856+10+6P(-2) = 32 + 8 - 56 + 10 + 6 P(2)=0P(-2) = 0

Thus, P(2)=0P(-2) = 0. By the Factor Theorem, this means x+2x + 2 is a factor of P(x)P(x), so 2-2 is a zero of P(x)P(x).

Step 2: Check if c=12c = \frac{1}{2} is a zero of P(x)P(x).

Now we evaluate P(12)P\left(\frac{1}{2}\right):

P(12)=2(12)4(12)314(12)25(12)+6P\left(\frac{1}{2}\right) = 2\left(\frac{1}{2}\right)^4 - \left(\frac{1}{2}\right)^3 - 14\left(\frac{1}{2}\right)^2 - 5\left(\frac{1}{2}\right) + 6

Calculating each term:

(12)4=116,(12)3=18,(12)2=14\left(\frac{1}{2}\right)^4 = \frac{1}{16}, \quad \left(\frac{1}{2}\right)^3 = \frac{1}{8}, \quad \left(\frac{1}{2}\right)^2 = \frac{1}{4}

P(12)=2(116)1814(14)5(12)+6P\left(\frac{1}{2}\right) = 2\left(\frac{1}{16}\right) - \frac{1}{8} - 14\left(\frac{1}{4}\right) - 5\left(\frac{1}{2}\right) + 6 P(12)=2161814452+6P\left(\frac{1}{2}\right) = \frac{2}{16} - \frac{1}{8} - \frac{14}{4} - \frac{5}{2} + 6 P(12)=1818352+6P\left(\frac{1}{2}\right) = \frac{1}{8} - \frac{1}{8} - \frac{35}{2} + 6 P(12)=0P\left(\frac{1}{2}\right) = 0

Thus, P(12)=0P\left(\frac{1}{2}\right) = 0. By the Factor Theorem, this means x12x - \frac{1}{2} is a factor of P(x)P(x), so 12\frac{1}{2} is a zero of P(x)P(x).

Step 3: Factor P(x)P(x) and find all other zeros.

Since x=2x = -2 and x=12x = \frac{1}{2} are zeros, P(x)P(x) can be factored as:

P(x)=(x+2)(x12)Q(x)P(x) = (x + 2)\left(x - \frac{1}{2}\right)Q(x)

To find the remaining zeros, we can perform polynomial division or factorization to find Q(x)Q(x), the remaining quadratic factor.

The complete factored form of P(x)P(x) is:

P(x)=(x+2)(2x1)(x23)P(x) = (x + 2)\left(2x - 1\right)(x^2 - 3)

Thus, the remaining zeros come from solving x23=0x^2 - 3 = 0:

x2=3x=±3x^2 = 3 \quad \Rightarrow \quad x = \pm \sqrt{3}

Final Answer:

The zeros of P(x)P(x) are: x=2,12,3,3x = -2, \frac{1}{2}, \sqrt{3}, -\sqrt{3}

Would you like further details or clarifications? Here are some related questions:

  1. How do you perform synthetic division to find polynomial factors?
  2. What is the Factor Theorem and how does it work?
  3. How do you solve higher-degree polynomials?
  4. How can you find zeros of polynomials graphically?
  5. What role does the discriminant play in finding zeros?

Tip: Always verify the potential zeros by substituting them back into the polynomial.

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Math Problem Analysis

Mathematical Concepts

Polynomial Functions
Zeros of a Function
Factoring

Formulas

P(x) = 2x^4 − x^3 − 14x^2 − 5x + 6
P(-2) = 2(-2)^4 − (-2)^3 − 14(-2)^2 − 5(-2) + 6
P(1/2) = 2(1/2)^4 − (1/2)^3 − 14(1/2)^2 − 5(1/2) + 6

Theorems

Factor Theorem

Suitable Grade Level

Grades 10-12