Nog meer andere koek van hetzelfde

$\eqalign{ & \int {\frac{{dx}} {{x\sqrt {x^2 + x + 1} }}} \cr & stel:\sqrt {x^2 + x + 1} = x + t \cr & noot: \cr & \sqrt {x^2 + x + 1} = x + t \cr & x^2 + x + 1 = (x + t)^2 \cr & x^2 + x + 1 = x^2 + 2tx + t^2 \cr & x + 1 = 2tx + t^2 \cr & x - 2tx = t^2 - 1 \cr & x(1 - 2t) = t^2 - 1 \cr & x = \frac{{t^2 - 1}} {{1 - 2t}} \cr & dus:x = \frac{{1 - t^2 }} {{2t - 5}} \cr & dx + dt = \left[ {\sqrt {x^2 + x + 1} } \right]' \cr & dx + dt = \frac{{2x + 1}} {{2\sqrt {x^2 + x + 1} }} \cr & 2\sqrt {x^2 + x + 1} dx + 2\sqrt {x^2 + x + 1} dt = 2x + 1 \cr & 2\sqrt {x^2 + x + 1} dt = 2x + 1 - 2\sqrt {x^2 + x + 1} dx \cr & dt = \frac{{2x + 1 - 2\sqrt {x^2 + x + 1} dx}} {{2\sqrt {x^2 + x + 1} }} \cr & noot: \cr & t = \sqrt {x^2 + x + 1} - x \cr & 2t = 2\sqrt {x^2 + x + 1} - 2x \cr & dus: \cr & dt = \frac{{\left( {1 - 2t} \right)dx}} {{2\sqrt {x^2 + x + 1} }} \cr & \frac{{dt}} {{1 - 2t}} = \frac{{dx}} {{2\sqrt {x^2 + x + 1} }} \cr & \frac{{2dt}} {{1 - 2t}} = \frac{{dx}} {{\sqrt {x^2 + x + 1} }} \cr & invullen: \cr & \int {\frac{{dx}} {{x\sqrt {x^2 + x + 1} }}} = \cr & 2\int {\frac{1} {x}} \cdot \left( {\frac{1} {{2\sqrt {x^2 + x + 1} }}} \right)dx = \cr & 2\int {\frac{{1 - 2t}} {{t^2 - 1}}} \cdot \frac{{dt}} {{1 - 2t}} = \cr & 2\int {\frac{{dt}} {{t^2 - 1}}} = \cr & \ln \left( {\frac{{t - 1}} {{t + 1}}} \right) = \cr & invullen: \cr & \ln \left( {\frac{{\left( {\sqrt {x^2 + x + 1} - x} \right) - 1}} {{\left( {\sqrt {x^2 + x + 1} - x} \right) + 1}}} \right) = \cr & \ln \left( {\frac{{x + 2 - 2\sqrt {x^2 + x + 1} }} {{3x}}} \right) \cr & conclusie: \cr & \int {\frac{{dx}} {{x\sqrt {x^2 + x + 1} }}} = \ln \left( {\frac{{x + 2 - 2\sqrt {x^2 + x + 1} }} {{3x}}} \right) + C_1 \cr & of \cr & \int {\frac{{dx}} {{x\sqrt {x^2 + x + 1} }}} = \ln \left( {\frac{{x + 2 - 2\sqrt {x^2 + x + 1} }} {x}} \right) + C_2 \cr}$