DIketahui (X-2) dan (X+1) adalah faktor faktor persamaan suku banyak X³+ax²+bx+10=0 Jika X1 X2 X3 adalah akar akar persamaan tersebut dengan X1 < X2 < X3 nilai

x - 2 = 0
x = 2
x³ + ax² + bx + 10 = 0
2³ + a.2² + b.2 + 10 = 0
8 + 4a + 2b + 10 = 0
4a + 2b = -18
2a + b = -9 ... (1)

x + 1 = 0
x = -1
x³ + ax² + bx + 10 = 0
(-1)² + a(-1)² + b(-1) + 10 = 0
-1 + a - b + 10 = 0
a - b = -9 ... (2)

jumlahkan persmaan (1) dan (2)
2a + a = -9 + (-9)
3a = -18
a = -6

a - b = -9
b = a + 9
b = 3

x³ + ax² + bx + 10 = 0
x³ - 6x² + 3x + 10 = 0
x1 = -1
x2 = 2

x1 + x2 + x3 = -b/a = -(-6)/1 = 6
(-1) + (2) + x3 = 6
x3 = 5

x1 < x2 < x3
-1 < 2 < 5 memenuhi

maka,

2x1 - x2 + x3
= 2(-1) - 2 + 5
= -2 - 2 + 5
= 1