+128407 x^3 - x^2 +5x - 5 = 0 factor as
x^2 ( x - 1) + 5 (x - 1) = 0
(x - 1) (x^2 + 5) = 0
So
x - 1 = 0 and x^2 + 5 = 0
x = 1 x^2 = - 5
x = ± i √ 5
The first answer is correct
7x^2 - 144 = -x^4 rearrange as
x^4 + 7x^2 - 144 = 0 factor as
(x^2 + 16) ( x^2 - 9) = 0
So
x^2 + 16 = 0 and x^2 - 9 = 9
x^2 = -16 x^2 = 9
x = ± 4i x = ±3
The third answer is correct
