Respuesta :

x^2 + x < 20
x^2 + x - 20 <0
set the left side equal 0

(x+5)(x-4) = 0
x + 5 = 0; x = -5
x - 4 = 0 ; x = 4

so solutions:
x has to be between -4 and 5 means
-5 < x < 4