Integral Rational 01E7Ab
1. Problem: Calculate the indefinite integral $$\int \frac{7x - 2}{x^2 - 1} dx$$.
2. Formula and rules: Use partial fraction decomposition since the denominator factors as $$x^2 - 1 = (x-1)(x+1)$$.
3. Decompose:
$$\frac{7x - 2}{(x-1)(x+1)} = \frac{A}{x-1} + \frac{B}{x+1}$$
Multiply both sides by $$x^2 - 1$$:
$$7x - 2 = A(x+1) + B(x-1)$$
4. Expand and group terms:
$$7x - 2 = A x + A + B x - B = (A + B) x + (A - B)$$
5. Equate coefficients:
For $$x$$: $$7 = A + B$$
For constant: $$-2 = A - B$$
6. Solve the system:
Add equations: $$7 + (-2) = (A + B) + (A - B) \Rightarrow 5 = 2A \Rightarrow A = \frac{5}{2}$$
Substitute $$A$$ into $$7 = A + B$$:
$$7 = \frac{5}{2} + B \Rightarrow B = 7 - \frac{5}{2} = \frac{9}{2}$$
7. Rewrite integral:
$$\int \frac{7x - 2}{x^2 - 1} dx = \int \frac{5/2}{x-1} dx + \int \frac{9/2}{x+1} dx$$
8. Integrate:
$$= \frac{5}{2} \int \frac{1}{x-1} dx + \frac{9}{2} \int \frac{1}{x+1} dx = \frac{5}{2} \ln|x-1| + \frac{9}{2} \ln|x+1| + C$$
Final answer:
$$\int \frac{7x - 2}{x^2 - 1} dx = \frac{5}{2} \ln|x-1| + \frac{9}{2} \ln|x+1| + C$$