Math Problem Statement

If x is small (1-x)^-5/2+(16+8x)^1/2÷(1+x)^-1/2(2+x)^2

Solution

We are asked to simplify or analyze the expression:

(1x)5/2+(16+8x)1/2(1+x)1/2(2+x)2(1 - x)^{-5/2} + \frac{(16 + 8x)^{1/2}}{(1 + x)^{-1/2}} \cdot (2 + x)^2

Let’s carefully simplify each part, considering xx is small. When xx is small, we can make use of approximations based on the binomial series expansion.


Step-by-Step Solution

1. Simplifying (1x)5/2(1 - x)^{-5/2} for small xx:

Use the binomial expansion for small xx: (1x)n1+nx+n(n1)2x2+(1 - x)^{n} \approx 1 + nx + \frac{n(n-1)}{2}x^2 + \dots Here n=5/2n = -5/2, so: (1x)5/21+(52)(x)+(52)(72)2x2+(1 - x)^{-5/2} \approx 1 + \left(-\frac{5}{2}\right)(-x) + \frac{\left(-\frac{5}{2}\right)\left(-\frac{7}{2}\right)}{2}x^2 + \dots (1x)5/21+52x+358x2+(1 - x)^{-5/2} \approx 1 + \frac{5}{2}x + \frac{35}{8}x^2 + \dots

2. Simplifying (16+8x)1/2(16 + 8x)^{1/2} for small xx:

We can factor out 16: (16+8x)1/2=16(1+12x)=4(1+12x)1/2(16 + 8x)^{1/2} = \sqrt{16(1 + \frac{1}{2}x)} = 4 \cdot (1 + \frac{1}{2}x)^{1/2} Now, use the binomial expansion again: (1+12x)1/21+1212x=1+14x(1 + \frac{1}{2}x)^{1/2} \approx 1 + \frac{1}{2} \cdot \frac{1}{2}x = 1 + \frac{1}{4}x Thus: (16+8x)1/24(1+14x)=4+x(16 + 8x)^{1/2} \approx 4 \left(1 + \frac{1}{4}x\right) = 4 + x

3. Simplifying (1+x)1/2(1 + x)^{-1/2} for small xx:

Using the binomial expansion for (1+x)1/2(1 + x)^{-1/2}: (1+x)1/2112x+(1 + x)^{-1/2} \approx 1 - \frac{1}{2}x + \dots

4. Simplifying the product with (2+x)2(2 + x)^2:

Expand (2+x)2(2 + x)^2: (2+x)2=4+4x+x2(2 + x)^2 = 4 + 4x + x^2

5. Putting it all together:

Now, the full second term becomes: (4+x)112x(4+4x+x2)\frac{(4 + x)}{1 - \frac{1}{2}x} \cdot (4 + 4x + x^2) For small xx, use the approximation 1112x1+12x\frac{1}{1 - \frac{1}{2}x} \approx 1 + \frac{1}{2}x: 4+x112x(4+x)(1+12x)=4+x+2x+12x2=4+3x+12x2\frac{4 + x}{1 - \frac{1}{2}x} \approx (4 + x)(1 + \frac{1}{2}x) = 4 + x + 2x + \frac{1}{2}x^2 = 4 + 3x + \frac{1}{2}x^2 Now multiply by 4+4x+x24 + 4x + x^2: (4+3x+12x2)(4+4x+x2)(4 + 3x + \frac{1}{2}x^2)(4 + 4x + x^2) Expanding: 16+16x+4x2+12x+12x2+32x3+2x2+2x3+12x416 + 16x + 4x^2 + 12x + 12x^2 + \frac{3}{2}x^3 + 2x^2 + 2x^3 + \frac{1}{2}x^4 Simplify the terms: 16+28x+18x2+72x3+12x416 + 28x + 18x^2 + \frac{7}{2}x^3 + \frac{1}{2}x^4


Final Expression:

Now, combining the two terms, we get: (1x)5/2+(16+28x+18x2+72x3+12x4)(1 - x)^{-5/2} + \left(16 + 28x + 18x^2 + \frac{7}{2}x^3 + \frac{1}{2}x^4\right) Using the earlier approximation for (1x)5/2(1 - x)^{-5/2}: 1+52x+358x2++16+28x+18x2+72x3+12x41 + \frac{5}{2}x + \frac{35}{8}x^2 + \dots + 16 + 28x + 18x^2 + \frac{7}{2}x^3 + \frac{1}{2}x^4

Simplify the combined terms: 17+(52+28)x+(358+18)x2+17 + \left(\frac{5}{2} + 28\right)x + \left(\frac{35}{8} + 18\right)x^2 + \dots 17+612x+1798x2+17 + \frac{61}{2}x + \frac{179}{8}x^2 + \dots


Conclusion:

The expression simplifies to: 17+612x+1798x2+17 + \frac{61}{2}x + \frac{179}{8}x^2 + \dots


Do you want further details or have any questions?


5 Related Questions:

  1. What is the binomial expansion, and when is it used?
  2. How does the approximation of small values work in calculus?
  3. What are higher-order terms in Taylor series expansions?
  4. How can we simplify complex algebraic fractions?
  5. What are common uses of fractional exponents in physics and engineering?

Tip:

When xx is small, binomial approximations are extremely useful for quick calculations. Remember to identify when higher-order terms are insignificant to avoid unnecessary complexity!

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Math Problem Analysis

Mathematical Concepts

Binomial Expansion
Algebraic Simplification
Series Expansion

Formulas

Binomial Expansion: (1 + x)^n ≈ 1 + nx + (n(n-1)/2)x^2 + ...
Algebraic Expansion: (a + b)^2 = a^2 + 2ab + b^2

Theorems

Binomial Theorem
Approximation for Small x

Suitable Grade Level

Grades 11-12 (Pre-Calculus or Calculus)