Answer :
If we substitute the correct value of x into the right side of the given expression, it should yield 192.
Test x = -8
(-8)^3 + 6(-8)^2 - 40(-8) = 192 Correct
Test x = -4
(-4)^3 + 6(-4)^2 - 40(-4) = 192 Correct
Test x = 6
6^3 + 6(6^2) - 40(6) = 192 Correct
All solutions make sense, so none of them should be eliminated.
Test x = -8
(-8)^3 + 6(-8)^2 - 40(-8) = 192 Correct
Test x = -4
(-4)^3 + 6(-4)^2 - 40(-4) = 192 Correct
Test x = 6
6^3 + 6(6^2) - 40(6) = 192 Correct
All solutions make sense, so none of them should be eliminated.