A(a):=-(5-5*a)^2/(2*a);

diff(A(a),a);

realroots(%);

a:-1;

A(-1);

kill(a);

plot2d([A(a)], [a,-2,0], [y,0,100],
 [plot_format, gnuplot])$

plot2d([A(a)], [a,-2,0], [y,0,100],
 [plot_format, gnuplot],
 [gnuplot_preamble, "set grid;"])$