(3x + 1)(2x - 5) = 39
3x(2x - 5) + 1(2x - 5) = 39
3x(2x) + 3x(-5) + 1(2x) + 1(-5) = 39
6x² + (-15x) + 2x + (-5) = 39
6x² - 15x + 2x - 5 = 39
6x² - 13x - 5 = 39
- 39 - 39
6x² - 13x - 44 = 0
x = -(-13) ± √((-13)² - 4(6)(-44))
2(6)
x = 13 ± √(169 + 1056)
12
x = 13 ± √(1225)
12
x = 13 ± 35
12
x = 13 + 35 ∨ x = 13 - 35
12 12
x = 48 ∨ x = -22
12 12
x = 4 ∨ x = -1⁵/₆
The solution set us equal to {4, -1⁵/₆}.