Do you know of any website that can solve quadratic inequalities?

Been a while since I’ve done math… I think the result set would be the unbounded interval (-∞, ∞) a.k.a the set of all real numbers.

But a web site to tell you that? Hmmmm…

They’d likely be running something like Maple or Mathematica.

I also would be interested if anyone turns something up.

—
[Edit]: you could write your equation as: x^2 – x – 4 >= 0

you could easily set it up at sagenb.com if you feel like learning sage. But you’d have to do the programming.

The answer is either <<-, -1.56]u[2,56, ->> or [-1.56]u[2.56, ->> .

Solve the quadratic inequality as you would do it if it were equal to 0. The values you get will be potential solutions, but if you evaluate the function at one and it you get something like 2 > 3, then you know that that value isn’t a solution.

For example if you had x^2 + 3 < -1, solve it as you would x^2 + 3 = -1. You would end up with x^2 +4 =0. Solve for x you get (x +2)^2 so your value for x in this case is ±2. Plug the values into the original x^2 + 3 < -1 and you will get (2)^2 +3 < -1 and (-2)^2 + 3 < -1. You will get 7 < -1 for both solutions, and since 7 is not less than -1, then there is no solution for that inequality.