WeBWorK Standalone Renderer

Take the conservative equation $x'' + 7 x^3 = 0$ .
How many critical points does the equation have:

Take the conservative equation $x'' + 3 x^2+1 = 0$ .
How many critical points does the equation have:

Take the conservative equation $x'' + x^{3}-7x^{2}-3x^{2}+21x = 0$ .
How many critical points does the equation have:

You can earn partial credit on this problem.