Convert the following mathematical expression to Python expression.

# Mathematical Expression Python Expression

$1$ D$=($cost$-$salvageValue$)/$Life

$2$ A$=\backslash$pi r$^2$

Note: $\backslash$pi $=3\mathrm{.}14$

$3$ F$=$C$\backslash$times $5/9+32$

$4$ x$=($b$^2-4$ac$)/2$a