Math Problem Statement

In the expansion of ( )( )6

2

1 2 1 1 k x k x x + + + , the coefficients of x and 2

x are 8 and 30 respectively. Find

the values of 1 k and 2

k.

Solution

Given the expansion of (1+k1x)(1+k2x)6(1 + k_1x)(1 + k_2x)^6, we are tasked with finding the values of k1k_1 and k2k_2 such that the coefficients of xx and x2x^2 are 8 and 30, respectively.

Step 1: Write the expansion for the first few terms

Expand (1+k1x)(1+k2x)6(1 + k_1x)(1 + k_2x)^6 using the binomial theorem for (1+k2x)6(1 + k_2x)^6:

(1+k2x)6=1+6k2x+15k22x2+(1 + k_2x)^6 = 1 + 6k_2x + 15k_2^2x^2 + \dots

Now multiply this by (1+k1x)(1 + k_1x):

(1+k1x)(1+6k2x+15k22x2+)(1 + k_1x)(1 + 6k_2x + 15k_2^2x^2 + \dots)

Step 2: Collect terms involving xx and x2x^2

  • The term involving xx comes from: 16k2x+k1x1=(6k2+k1)x1 \cdot 6k_2x + k_1x \cdot 1 = (6k_2 + k_1)x The coefficient of xx is 6k2+k1=86k_2 + k_1 = 8.

  • The term involving x2x^2 comes from: 115k22x2+k1x6k2x=(15k22+6k1k2)x21 \cdot 15k_2^2x^2 + k_1x \cdot 6k_2x = (15k_2^2 + 6k_1k_2)x^2 The coefficient of x2x^2 is 15k22+6k1k2=3015k_2^2 + 6k_1k_2 = 30.

Step 3: Solve the system of equations

We now have two equations:

  1. 6k2+k1=86k_2 + k_1 = 8
  2. 15k22+6k1k2=3015k_2^2 + 6k_1k_2 = 30

From equation (1):

Solve for k1k_1: k1=86k2k_1 = 8 - 6k_2

Substitute this into equation (2):

15k22+6(86k2)k2=3015k_2^2 + 6(8 - 6k_2)k_2 = 30

Simplify: 15k22+48k236k22=3015k_2^2 + 48k_2 - 36k_2^2 = 30 21k22+48k230=0-21k_2^2 + 48k_2 - 30 = 0

Divide through by -3 to simplify: 7k2216k2+10=07k_2^2 - 16k_2 + 10 = 0

Step 4: Solve the quadratic equation

Solve using the quadratic formula: k2=(16)±(16)24(7)(10)2(7)k_2 = \frac{-(-16) \pm \sqrt{(-16)^2 - 4(7)(10)}}{2(7)} k2=16±25628014k_2 = \frac{16 \pm \sqrt{256 - 280}}{14} k2=16±2414k_2 = \frac{16 \pm \sqrt{-24}}{14}

The discriminant is negative, indicating no real solution for k2k_2. Please recheck the values given or the setup of the problem.

Would you like me to explain this in more detail or check for any possible corrections?


Here are 5 questions based on this problem:

  1. How does the binomial theorem apply to expanding expressions like (1+k2x)6(1 + k_2x)^6?
  2. Can you describe how coefficients of specific terms like xx or x2x^2 are identified during expansion?
  3. Why is the quadratic formula used to solve for k2k_2, and what happens when there is a negative discriminant?
  4. How would the process change if the discriminant were positive?
  5. What are the implications of having no real solutions for this system of equations?

Tip: Always check the discriminant when solving quadratic equations to predict whether you'll get real, repeated, or complex roots.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Binomial Expansion
Algebra
Quadratic Equations

Formulas

Binomial Expansion formula: (1 + kx)^n = 1 + nkx + (n(n-1)/2)k^2x^2 + ...
Quadratic equation formula: ax^2 + bx + c = 0

Theorems

Binomial Theorem
Quadratic Formula

Suitable Grade Level

Grades 10-12