Jawab:

1a. uraikan dulu ruas kanannya, lalu setarakan dgn angka di ruas kiri

3x² + 2x -5 = (ax+1)(x+b) - c(x+1) + 2(ab-c)

                  = ax² + x + abx - cx - c + 2ab - 2c

                  = ax² + (x + abx - cx) + (- c + 2ab - 2c)

3x² + 2x -5 = ax² + (1 + ab - c)x + (2ab - 3c)

∴ a = 3

1+ab-c = 2

1+3b-c = 2

3b-c = 1

6b - 2c = 2

6b = 2c + 2 --> persamaan 1

2ab-3c = -5

2(3)b-3c = -5

6b - 3c = -5 --> substitusi persamaan 1

2c + 2 - 3c = -5

c = 7

3b-c = 1

3b-7 = 1

b = 8/3

b. gabungkan dulu ruas kanan, lalu setarakan dgn ruas kiri

3x² + 2x -5 = ax² - ax - 6a + bx² - 2bx - 15b + 4c

3x² + 2x -5 = (a+b)x² +(-a-2b)x +(-6a -15b+4c)

a+b = 3

-a-2b = 2

--------------- (+)

-b = 5

b = 5

a+b = 3

a+5 = 3

a = -2

-6a-15b+4c = -5

-6(-2) - 15(5) + 4c = -5

4c = 58

c = 14,5