I think it is -8. Subsitute the value. 2(-8) +1=-15 which is less than 0. When you plug -8 for x^2 -1 you get 64-1 which is 63. 63 is offcourse greater than 0.
I think it is -8. Subsitute the value. 2(-8) +1=-15 which is less than 0. When you plug -8 for x^2 -1 you get 64-1 which is 63. 63 is offcourse greater than 0.