Sameerkale

Partial Fractions

Often you will see expressions with two factors in the denominator, where it is necessary or at least beneficial to change the expression into two terms with one factor in the denominator of each. Here's how to do it:

1. Set it up like this: ${\frac {\mathit {k}}{\left(x+\alpha \right)\left(x+\beta \right)}}={\frac {A}{\left(x+\alpha \right)}}+{\frac {B}{\left(x+\beta \right)}}$ 2. Set it in terms of k: ${\mathit {k}}=A\left(x+\beta \right)+B\left(x+\alpha \right)$

${\begin{matrix}x=-\alpha \\\therefore {\mathit {k}}=B(\beta -\alpha )\\\therefore B={\frac {\mathit {k}}{(\beta -\alpha )}}\end{matrix}}$

Engine: $W=\int _{V_{i}}^{V_{f}}P\ dV\ ={\frac {-nRT}{A}}\int _{l_{i}}^{l_{f}}1/l\ dl\ ={\frac {-nRT}{A}}ln(l_{f}/l_{i})$ $W=F\Delta l$