Question

Answer 1

\(x=7\Leftrightarrow x+1=8\)

Thay vào biểu thức:

\(=x^{15}-\left(x+1\right)x^{14}+\left(x+1\right)x^{13}-\left(x+1\right)x^{12}+...-\left(x+1\right)x^2+\left(x+1\right)x-5\\ =x^{15}-x^{15}-x^{14}+x^{14}+x^{13}-x^{13}-x^{12}+...-x^3-x^2+x^2+x-5\\ =x-5=7-5=2\)

Answer 2

x=7

nên x+1=8

\(A=x^{15}-8x^{14}+8x^{13}-...-8x^2+8x-5\)

\(=x^{15}-x^{14}\left(x+1\right)+x^{13}\left(x+1\right)-...-x^2\left(x+1\right)+x\left(x+1\right)-5\)

=x-5

=7-5=2