(x+2)(x+1)(x-2)(x-1) = 0
or
(x^2-4)(x^2-1) = 0
or
x^4 -5x^2 + 4 = 0
just take each zero and change its sign, then add it to x, such as the zero 2 has the factor x-2
the zero -2 has the factor x--2 or x+2, zero 1 has factor x-1, zero -1 has the factor x--1 = x+2
multiply the 4 factors together and set them = 0