Jika (ax+3)(bx+c)=6x²+5x-6,maka nilai 3b =

Bab Persamaan Kuadrat
Matematika SMP Kelas VIII

(ax + 3) (bx + c) = abx² + acx + 3bx + 3c
                           = abx² + (ac + 3b) x + 3c

6x² + 5x - 6 = abx² + (ac + 3b) x + 3c

3c = -6
c = -6/3
c = -2

ac + 3b = 5
a. (-2) + 3b = 5
-2a + 3b = 5

ab = 6
a = 6/b

-2a + 3b = 5
-2 . 6/b + 3b = 5

**dikalikan b**
-12 + 3b² = 5b
3b² - 5b - 12 = 0
(3b + 4) (b - 3) = 0
3b + 4 = 0
3b = -4

maka, 3b = -4