Math Problem Statement

For what value of c will the polynomial P(x) = -2x3 + cx2 - 5x + 2 have the same remainder when it is divided by x - 2 and by x + 1?

Solution

We are given the polynomial P(x)=2x3+cx25x+2P(x) = -2x^3 + cx^2 - 5x + 2, and we need to find the value of cc such that the remainder is the same when divided by x2x - 2 and x+1x + 1.

According to the Remainder Theorem, the remainder when a polynomial P(x)P(x) is divided by xax - a is P(a)P(a). Therefore, the remainder when divided by x2x - 2 is P(2)P(2), and the remainder when divided by x+1x + 1 is P(1)P(-1).

We are told that these remainders are equal, so:

P(2)=P(1)P(2) = P(-1)

Step 1: Calculate P(2)P(2)

Substitute x=2x = 2 into P(x)P(x):

P(2)=2(2)3+c(2)25(2)+2P(2) = -2(2)^3 + c(2)^2 - 5(2) + 2 P(2)=2(8)+c(4)10+2P(2) = -2(8) + c(4) - 10 + 2 P(2)=16+4c10+2P(2) = -16 + 4c - 10 + 2 P(2)=4c24P(2) = 4c - 24

Step 2: Calculate P(1)P(-1)

Substitute x=1x = -1 into P(x)P(x):

P(1)=2(1)3+c(1)25(1)+2P(-1) = -2(-1)^3 + c(-1)^2 - 5(-1) + 2 P(1)=2(1)+c(1)+5+2P(-1) = -2(-1) + c(1) + 5 + 2 P(1)=2+c+5+2P(-1) = 2 + c + 5 + 2 P(1)=c+9P(-1) = c + 9

Step 3: Set P(2)=P(1)P(2) = P(-1)

Now, set the two expressions equal to each other:

4c24=c+94c - 24 = c + 9

Step 4: Solve for cc

Subtract cc from both sides:

3c24=93c - 24 = 9

Add 24 to both sides:

3c=333c = 33

Finally, divide by 3:

c=11c = 11

Thus, the value of cc that makes the remainders equal is 11\boxed{11}.

Would you like further details or have any questions?

Here are 5 related questions to explore:

  1. How does the Remainder Theorem work for polynomials?
  2. What is the significance of the factorization of a polynomial?
  3. How would the remainder change if divided by other linear factors like x3x - 3?
  4. Can synthetic division be used to solve similar problems, and how?
  5. How does the value of cc affect the graph of the polynomial?

Tip: When working with polynomials and the Remainder Theorem, always substitute carefully to avoid errors, especially with negative signs.

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Math Problem Analysis

Mathematical Concepts

Polynomials
Remainder Theorem
Algebraic Substitution

Formulas

P(a) = remainder when P(x) is divided by x - a

Theorems

Remainder Theorem

Suitable Grade Level

Grades 10-12