Math Problem Statement

(3x2+2x+1)2x2+3x+2\int\frac{\left(3x^2+2x+1\right)}{\sqrt{2x^2+3x+2}}

Solution

To evaluate the integral

3x2+2x+12x2+3x+2dx,\int \frac{3x^2 + 2x + 1}{\sqrt{2x^2 + 3x + 2}} \, dx,

we can use a combination of substitution and simplification steps. Here is the solution step by step:


Step 1: Simplify the quadratic expression in the denominator

The denominator 2x2+3x+2\sqrt{2x^2 + 3x + 2} can be factored:

2x2+3x+2=(2x+1)(x+2).2x^2 + 3x + 2 = (2x + 1)(x + 2).

Thus, the integral becomes:

3x2+2x+1(2x+1)(x+2)dx.\int \frac{3x^2 + 2x + 1}{\sqrt{(2x + 1)(x + 2)}} \, dx.


Step 2: Split the numerator

Notice that the degree of the numerator is higher than that of the denominator. To simplify, perform polynomial division. Divide 3x2+2x+13x^2 + 2x + 1 by 2x2+3x+22x^2 + 3x + 2:

  1. Divide the leading terms: 3x22x2=32\frac{3x^2}{2x^2} = \frac{3}{2}.
  2. Multiply back and subtract: (3x2+2x+1)32(2x2+3x+2)=52x2.(3x^2 + 2x + 1) - \frac{3}{2}(2x^2 + 3x + 2) = -\frac{5}{2}x - 2.

So, the fraction becomes:

3x2+2x+1(2x+1)(x+2)=321(2x+1)(x+2)+52x2(2x+1)(x+2).\frac{3x^2 + 2x + 1}{\sqrt{(2x + 1)(x + 2)}} = \frac{3}{2} \cdot \frac{1}{\sqrt{(2x + 1)(x + 2)}} + \frac{-\frac{5}{2}x - 2}{\sqrt{(2x + 1)(x + 2)}}.

Thus, the integral splits into two parts:

3x2+2x+1(2x+1)(x+2)dx=321(2x+1)(x+2)dx+52x2(2x+1)(x+2)dx.\int \frac{3x^2 + 2x + 1}{\sqrt{(2x + 1)(x + 2)}} \, dx = \frac{3}{2} \int \frac{1}{\sqrt{(2x + 1)(x + 2)}} \, dx + \int \frac{-\frac{5}{2}x - 2}{\sqrt{(2x + 1)(x + 2)}} \, dx.


Step 3: Solve each term

(a) First integral:

The first term requires a substitution. Let:

u=2x2+3x+2,so that du=(4x+3)dx.u = 2x^2 + 3x + 2, \quad \text{so that } \, du = (4x + 3) \, dx.

The integral simplifies, but we would need to evaluate it explicitly.

(b) Second integral:

The second term can also be evaluated using similar techniques or trigonometric substitution.


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Math Problem Analysis

Mathematical Concepts

Integral Calculus
Polynomial Division
Substitution
Trigonometric Substitution

Formulas

Polynomial division for simplifying expressions
Substitution: u-substitution with du
Square root simplification involving quadratic expressions

Theorems

Integration by substitution

Suitable Grade Level

Undergraduate Calculus