For the equation  x2+x-6=0, the roots are

When x<0, x=-x∴Equation is x2-x-6=0⇒x=-2,3∵x<0, ∴x=-2 is the solution.When x≥0, x=x∴Equation is x2+x-6=0⇒x=2, -3∵x≥0, ∴x=2 is the solution.Hence x=2, -2 are the solutions and their sum is zero.