B=x7 - 26x6 + 27x5 - 47x4 - 73x3 + 50x2 + x - 24
= x7 - ( x + 1 ) x6 + ( x +2 )x5 - ( 2x - 3 )x4 - ( 3x - 2 ) x3 + 2x .x2 + x - ( x - 1 )
= x7 - x7 - x6 + x6 + 2x5 - 2x5 + 3x4 - 3x4 + 2x3 + 2x3 + x - x - 1
= 4x3 -1
Thay x = 25
4x3 - 1
= 4. 253 - 1
= 4. 15625 - 1
= 62500 -1 = 62499