2x³ + ax² - bx +3 dibagi x²-4 sisa x+23 maka nilai a+b =......

x² - 4 = (x + 2)(x - 2)

x = 2
2x³ + ax² - bx + 3 = x + 23
2.2³ + a.2² - b.2 + 3 = 2 + 23
4a - 2b = 6
2a - b = 3 ... (1)

x = -2
2x³ + ax² - bx + 3 = x + 23
-16 + 4a + 2b + 3 = -2 + 23
2a + b = 17 ... (2)

Jumlahkan (1) dan (2)
4a = 3 + 17
a = 5

2a + b = 17
b = 7

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a + b = 12 ✓