Answer:
we have:
8x³ + mx² - 6x + n
= 8x³ - 8x² + (m + 8)x²- (m + 8)x + (m + 2)x - (m + 2) + m + 2+ n
= 8x²(x - 1) + (m + 8)x(x - 1) + (m + 2)(x - 1) + (m + n + 2)
= (x - 1)[8x² + (m + 8)x + m + 2] + (m + n + 2)
because the remainder if divided by (x-1) is 2
=> m + n + 2 = 2
⇔ m + n = 0 (1)
we also have:
8x³ + mx² - 6x + n
= 8x³ - 12x² + (m + 12)x² - 3/2.x.(m + 12) + ( 12 + 3/2.m)x - (9/4.m + 18) + n +9/4m + 18
= 4x²(2x - 3) + 1/2.(m + 12)x(2x - 3) + (3/2m + 12).1/2.(2x - 3) + 9/4m + n + 18
= (2x - 3)(4x² + (m + 12)/2.x + 3/4m + 6) + 9/4m + n + 18
because the remainder if divided by (2x - 3) is 8
=> 9/4m + n + 18 = 8
⇔ 9/4m + n = -10 (2)
from (1) and (2), we have:
m + n = 0
9/4m + n = -10
=> m = -8
n = 8
Explanation: