Answer: the zeros are x = {-5, -3, 2, 4}
Explanation:
x⁴ + 2x³ - 25x² - 26x + 120 = 0
Given: x = 2 and x = 4
Use synthetic division to find the reduced polynomial for x = 2 and then x = 4
2 | 1 2 -25 -26 120
| ↓ 2 8 -34 -120
1 4 -17 -60 0 ← remainder
4 | 1 4 -17 -60
| ↓ 4 32 60
1 8 15 0 ← remainder
1x² + 8x + 15 = 0
(x + 5) (x + 3) = 0
x + 5 = 0 x + 3 = 0
x = -5 x = -3
The zeros are: x = 2, x = 4, x = -5, and x = -3