(х^2+х)*(х^2+х-5)=84

(x^2+x-5)(x^2+x) = 84

x^4+2x^3-4x^2-5x = 84

x^4+2x^3-4x^2-5x-84 = 0

(x-3)(x+4)(x^2+x+7) = 0

x = 3 or x = -4 or x^2+x+7 = 0

x = 3 or x = -4