1) (z - 2)³ - z²(z - 6) = 13z - 7
z³ - 3 * z² * 2 + 3 * z * 2² - 2³- z³ + 6z² = 13z - 7
z³ - 6z² + 12z - 8 - z³+ 6z² - 13z + 7 = 0
- z = 1
z = -1
2) (3 - t)³ + 3t + 21 = - t²(t - 9)
3³ - 3 * 3² * t + 3 * 3 * t² - t³ + 3t + 21 = - t³ + 9t²
27 - 27t + 9t² - t³ + t³ - 9t² + 3t + 21= 0
- 24t = - 48
t = 2