# Example 1
 eq:=x^2+4*x+6:
 ans:=[solve(eq=0,x)];
 eq1:=(x-ans[1])*(x-ans[2])=0;
 expand(eq1);

# Example 2
f:=x->x^2+5*x+6:
a:=-4: b:=-1:
plot(f(x),x=a..b);