Math Problem Statement

(x - 4)P(x) = x^3 - 2x^2 + ax + b. Find the value of b.

Solution

The equation in the image shows:

(x4)P(x)=x32x2+ax+b(x - 4) \cdot P(x) = x^3 - 2x^2 + ax + b

We are asked to determine the value of bb.

To solve this, let's express P(x)P(x) as a polynomial and use polynomial division or equating coefficients. Let P(x)P(x) be a quadratic polynomial:

P(x)=x2+px+qP(x) = x^2 + px + q

Now, expand (x4)P(x)(x - 4) \cdot P(x):

(x4)(x2+px+q)=x3+px2+qx4x24px4q(x - 4)(x^2 + px + q) = x^3 + px^2 + qx - 4x^2 - 4px - 4q

Simplify the expression:

x3+(p4)x2+(q4p)x4qx^3 + (p - 4)x^2 + (q - 4p)x - 4q

Now, compare this with the original equation:

x32x2+ax+bx^3 - 2x^2 + ax + b

By equating the coefficients of the corresponding powers of xx, we get the following system of equations:

  1. Coefficient of x2x^2: p4=2p - 4 = -2p=2p = 2
  2. Coefficient of x1x^1: q4p=aq - 4p = aq8=aq - 8 = a
  3. Constant term: 4q=b-4q = b

Now, we know that p=2p = 2, so substitute into the third equation for bb:

4q=b-4q = b

Thus, b=4qb = -4q.

If you would like further clarification or details on the next steps, feel free to ask!

Here are some related questions to consider:

  1. What happens if we try a different degree for P(x)P(x)?
  2. How does the value of aa affect the function in this equation?
  3. Could there be multiple values for bb in similar polynomial equations?
  4. How can polynomial long division help in these types of problems?
  5. What if the given equation had no constant term—how would that affect P(x)P(x)?

Tip: Always align the degrees of terms when expanding polynomial expressions for easier comparison.

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Math Problem Analysis

Mathematical Concepts

Polynomial Expansion
Algebra
Polynomial Equations

Formulas

(x - 4)(P(x)) = x^3 - 2x^2 + ax + b
Comparing coefficients of polynomials
General form of a quadratic P(x) = x^2 + px + q

Theorems

Polynomial comparison to find unknown coefficients

Suitable Grade Level

Grades 10-12