Part of CALC-10 — Integration: Advanced Techniques & Reduction

Integration of Type integral (px+q)/sqrt(ax^2+bx+c) dx

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Method: Write px+q = A * d/dx(ax2+bx+cax^{2+bx+c}) + B = A(2ax+b) + B. Solve for A and B: 2aA = p, Ab + B = q. So A = p2a\frac{p}{2a}, B = q - bp2a\frac{bp}{2a}.

Split the integral: integral px+qsqrt\frac{px+q}{sqrt}(ax2+bx+cax^{2+bx+c}) dx = A * integral 2ax+bsqrt\frac{2ax+b}{sqrt}(ax2+bx+cax^{2+bx+c}) dx + B * integral dx/sqrt(ax2+bx+cax^{2+bx+c})

First integral: integral 2ax+bsqrt\frac{2ax+b}{sqrt}(ax2+bx+cax^{2+bx+c}) dx = 2*sqrt(ax2+bx+cax^{2+bx+c}) + C (since the numerator is the derivative of the expression under the root)

Second integral: Complete the square and use standard forms:

  • integral dx/sqrt(X^{2+k}^2) = ln|X+sqrt(X^{2+k}^2)| + C
  • integral dx/sqrt(k^{2-X}^2) = arcsinXk\frac{X}{k} + C
  • integral dx/sqrt(X^{2-k}^2) = ln|X+sqrt(X^{2-k}^2)| + C

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