Math Problem Statement

Polinomial ax^4 - 13x^3 + 27x^2 - 38x + b mempunyai faktor x^2 - 6x + 8. Nilai a + b adalah?

Solution

The given problem involves the polynomial ax413x3+27x238x+bax^4 - 13x^3 + 27x^2 - 38x + b, which has x26x+8x^2 - 6x + 8 as a factor. You are asked to find the value of a+ba + b.

Solution:

Since x26x+8x^2 - 6x + 8 is a factor, the polynomial can be divided by this quadratic. Let's factor x26x+8x^2 - 6x + 8:

x26x+8=(x2)(x4)x^2 - 6x + 8 = (x - 2)(x - 4)

Now, we express the polynomial ax413x3+27x238x+bax^4 - 13x^3 + 27x^2 - 38x + b as:

(ax413x3+27x238x+b)=(x26x+8)(qx2+rx+s)(ax^4 - 13x^3 + 27x^2 - 38x + b) = (x^2 - 6x + 8)(qx^2 + rx + s)

Expanding the product:

(x26x+8)(qx2+rx+s)=qx4+rx3+sx26qx36rx26sx+8qx2+8rx+8s(x^2 - 6x + 8)(qx^2 + rx + s) = qx^4 + rx^3 + sx^2 - 6qx^3 - 6rx^2 - 6sx + 8qx^2 + 8rx + 8s

Now, let's collect terms:

=qx4+(r6q)x3+(s6r+8q)x2+(6s+8r)x+8s= qx^4 + (r - 6q)x^3 + (s - 6r + 8q)x^2 + (-6s + 8r)x + 8s

We compare this with the original polynomial ax413x3+27x238x+bax^4 - 13x^3 + 27x^2 - 38x + b, which gives the following system of equations:

  1. q=aq = a
  2. r6q=13r - 6q = -13
  3. s6r+8q=27s - 6r + 8q = 27
  4. 6s+8r=38-6s + 8r = -38
  5. 8s=b8s = b

Solving the system:

From equation (1): q=aq = a

From equation (2): r6a=13r=6a13r - 6a = -13 \quad \Rightarrow \quad r = 6a - 13

Substitute r=6a13r = 6a - 13 into equation (3):

s6(6a13)+8a=27s - 6(6a - 13) + 8a = 27 s36a+78+8a=27s - 36a + 78 + 8a = 27 s28a+78=27s=28a51s - 28a + 78 = 27 \quad \Rightarrow \quad s = 28a - 51

Substitute s=28a51s = 28a - 51 and r=6a13r = 6a - 13 into equation (4):

6(28a51)+8(6a13)=38-6(28a - 51) + 8(6a - 13) = -38 168a+306+48a104=38-168a + 306 + 48a - 104 = -38 120a+202=38120a=240a=2-120a + 202 = -38 \quad \Rightarrow \quad -120a = -240 \quad \Rightarrow \quad a = 2

Substitute a=2a = 2 into the expressions for rr and ss:

r=6(2)13=1213=1r = 6(2) - 13 = 12 - 13 = -1 s=28(2)51=5651=5s = 28(2) - 51 = 56 - 51 = 5

Now, use equation (5) to find bb:

8s=b8(5)=bb=408s = b \quad \Rightarrow \quad 8(5) = b \quad \Rightarrow \quad b = 40

Finally, a+b=2+40=42a + b = 2 + 40 = 42.

Thus, the value of a+ba + b is 42\boxed{42}.

Would you like more details on any of these steps? Here are five additional questions to explore:

  1. How do you factor polynomials using synthetic division?
  2. What methods can you use to check if a quadratic is a factor of a polynomial?
  3. How do you derive the system of equations for polynomial division?
  4. What are other ways to solve for coefficients in polynomial factorization?
  5. How do you expand and simplify products of polynomials?

Tip: When comparing coefficients in polynomials, always organize terms carefully to avoid errors.

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Math Problem Analysis

Mathematical Concepts

Polynomial Factorization
Algebra

Formulas

Polynomial Division
Factorization

Theorems

Factor Theorem

Suitable Grade Level

Grades 10-12