✔ 最佳答案
2z² + 5z - 18 = 0
2z² + 5z = 18
z² + 5/2z = 9
z² + 5/4z = 9 + (5/4)²
z² + 5/4z = 144/16 + 25/16
(z + 5/4)² = 169/16
z + 5/4 = ± 13/4
Factors (horizontally presented):
= z + 5/4 - 13/4, = z - 8/4, = z - 2
= z + 5/4 + 13/4, = z + 18/4, = z + 9/2, = 2z + 9
Answer: (z - 2)(2z + 9)