Question

Bài 1: Tính f(7) biết: f(x)= \(-x^{15}+8x^{14}-8x^{13}+8x^{12}-8x^{11}+....+8x^2-8x-5\)

GIÚP MIK VS!!! MIK ĐAG CẦN RẤT GẤP

Answer 1

Bài 1:

\(f\left(x\right)=-x^{15}+8x^{14}-8x^{13}+...-8x-5\)

Ta xét \(x=7\Leftrightarrow x+1=8\)

Khi đó :

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

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

\(f\left(7\right)=-x-5\)

\(f\left(7\right)=-7-5\)

\(f\left(7\right)=-12\)

Vậy...