4. Which of the following is not a factor of \( 5 x ^ { 3 } - 80 x \) ?
(1) \( 5 x \) (3) \( x - 4 \) (2) \( x - 8 \) (4) \( x ^ { 2 } - 16\)
4. Which of the following is not a factor of \( 5 x ^ { 3 } - 80 x \) ?
(1) \( 5 x \) (3) \( x - 4 \) (2) \( x - 8 \) (4) \( x ^ { 2 } - 16\)