X intercepts means y = 0.
So, just equals the equation to 0 and solve for x.
For example, if the equation is a parabola, y = ax^2 + bx + c, make
ax^2 + bx + c = 0.
You can solve that equation using the quadratic formula:
- b +/- √ [ b^2 - 4(a)(c) ]
x = --------------------------------
2(a)
Replacing a, b and c will give you the roots of the polynomial which are the x-intercepts.