tìm biểu thức a= x^6 - 20x^5 20x^4
Giải thích
Ta có: x = 21 nên x – 1 = 20
A = x6 – 20x5 – 20x4 – 20x3 – 20x2 – 20x + 3
A = x6 – x5(x – 1) – x4(x – 1) – x3(x – 1) – x2(x – 1) – x(x – 1) + 3
A = x6 – x6 + x5 – x5 + x4 – x4 + x3 – x3 + x2 – x2 + x + 3
A = x + 3
A = 21 + 3
A = 24.