Math Problem Statement

If the ratio of the terms equidistant from the middle term in the expansion of (1 + x) ^ 12 is 1/256 * (x \in N) then sum of all the terms of the expansion (1 + x) ^ 12 is

Solution

To solve this problem, let's analyze it step by step:

1. Understand the Problem

The expansion of (1+x)12(1 + x)^{12} follows the binomial theorem:

(1+x)12=k=012(12k)xk(1 + x)^{12} = \sum_{k=0}^{12} \binom{12}{k} x^k

The terms equidistant from the middle in this expansion are Tr=(12r)xrT_r = \binom{12}{r} x^r and T12r=(1212r)x12rT_{12-r} = \binom{12}{12-r} x^{12-r}.

The ratio of these terms is given as:

TrT12r=(12r)xr(1212r)x12r\frac{T_r}{T_{12-r}} = \frac{\binom{12}{r} x^r}{\binom{12}{12-r} x^{12-r}}

Simplify the ratio:

Since (12r)=(1212r)\binom{12}{r} = \binom{12}{12-r}, the ratio becomes:

TrT12r=xrx12r=x2r12\frac{T_r}{T_{12-r}} = \frac{x^r}{x^{12-r}} = x^{2r - 12}

We are given that this ratio equals 1256\frac{1}{256}, so:

x2r12=1256x^{2r - 12} = \frac{1}{256}

Express 1256\frac{1}{256} as a power of 2:

1256=28\frac{1}{256} = 2^{-8}

Thus:

x2r12=28x^{2r - 12} = 2^{-8}

Take logarithms to solve for xx:

2r12=8    2r=4    r=22r - 12 = -8 \implies 2r = 4 \implies r = 2

2. Sum of All Terms

The sum of all terms in the binomial expansion (1+x)12(1 + x)^{12} is obtained by substituting x=1x = 1 into the expansion:

Sum=(1+1)12=212=4096\text{Sum} = (1 + 1)^{12} = 2^{12} = 4096

Final Answer:

The sum of all the terms in the expansion is 4096.


Would you like more details or have any questions?

Here are 5 related questions for further exploration:

  1. How do you find the rr-th term in a binomial expansion?
  2. What is the middle term of (1+x)12(1 + x)^{12}?
  3. How does the ratio of equidistant terms change if x1x \neq 1?
  4. What is the general formula for the sum of all terms in (1+x)n(1 + x)^n?
  5. Can you derive properties of coefficients using equidistant terms in the binomial expansion?

Tip: For ratios involving equidistant terms, consider the symmetry of binomial coefficients!

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Math Problem Analysis

Mathematical Concepts

Binomial Expansion
Algebra
Exponents

Formulas

Binomial theorem: (a + b)^n = Σ (nCr * a^(n-r) * b^r)
Sum of all terms in (1 + x)^n: Substitute x = 1 into the expansion

Theorems

Binomial Theorem
Symmetry of binomial coefficients

Suitable Grade Level

Grades 11-12