Quadratic equation in TeX

Example for versions Web2c 2009

This example uses TeX fixed point arithmetic package fp and it’s macro for solving quadratic equations called \FPqsolve. Note that this macro can find only real roots of equation, and prints “FP error: Quadratic equation does not have a solution” if roots are complex (i.e., non-existent from its point of view). 

\input fp.tex

\message{A = }
\read -1 to \a
\message{B = }
\read -1 to \b
\message{C = }
\read -1 to \c

\FPqsolve{\xone}{\xtwo}{\number\a}{\number\b}{\number\c}

$\a x^2+\b x+\c=0$

$x_1=\xone$

$x_2=\xtwo$
\bye

Quadratic equation: document generated by TeX example program
Quadratic equation: document generated by TeX example program