tinh x^10+2017x^9-2017x^8-2017x^7+...........+2017x^2-2017x+2017 voi x=2016
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Lời giải:
Tại $x=2016$ thì $x-2016=0$
Khi đó:
$A=x^{2016}(x-2016)-x^{2015}(x-2016)+x^{2014}(x-2016)-x^{2013}(x-2016)+.....-x(x-2016)+x-2017$
$=x^{2016}.0-x^{2015}.0+......-x.0+2016-2017=2016-2017=-1$
Dễ thầy 2017=2016+1=x+1
Thay vào ta có:
\(x^{10}-2017x^9+2017x^8-.....+2017x^2-2017x+2017\)
\(=x^{10}-\left(x+1\right)x^9+\left(x+1\right)x^8-....+\left(x+1\right)x^2-\left(x+1\right)x+2017\)
\(=x^{10}-x^{10}-x^9+x^9+x^8-....+x^3+x^2-x^2-x+2017=-x+2017=-2016+2017=1\)
Vậy..........
f(2016)=20168 - 2017*20167 +2017*20166 - 2017*20165 +...+2017*20162 - 2017*2016+ 2018
=20168 -( 20168 + 2016) + (20167+2016) - (20166 + 2016)+....+20163+2016 -( 20162 + 2016)+2018
=2018
Thay x=2016 thì 2017=x+1 và 2018=x+2 Do đó
\(f\left(x\right)=x^8-\left(x+1\right)x^7+\left(x+1\right)x^6-...-\left(x+1\right)x\)\(+x+2\)
\(=x^8-x^8-x^7+x^7+x^6-...+x^2-x^2-x+x+2\)
\(=2\)
f(2016)=2016^8 - 2017*2016^7 +2017*2016^6 - 2017*2016^5 +...+2017*2016^2 - 2017*2016+ 2018
=2016^8 -( 2016^8 + 2016) + (2016^7+2016) - (2016^6 + 2016)+....+2016^3+2016 -( 2016^2 + 2016)+2018
=2018
mình đọc chả hiểu gì
có bạn nào giải chi tiết ra được không
x=2016 nên x+1=2017
\(f\left(x\right)=x^{99}-x^{98}\left(x+1\right)+x^{97}\left(x+1\right)-...-x^2\left(x+1\right)+x\left(x+1\right)-1\)
\(=x^{99}-x^{99}-x^{98}+x^{98}+x^{97}-x^{97}+...-x^3-x^2+x^2+x-1\)
=x-1=2015
\(f\left(x\right)=x^{99}-2017x^{98}+2017x^{97}-...+2017x-1\)
\(=x^{99}-2016x^{98}-x^{98}+2016x^{97}+...-x^2+2016x+x-2016+2015\)
\(=x^{98}\left(x-2016\right)-x^{97}\left(x-2016\right)+...-x\left(x-2016\right)+\left(x-2016\right)+2015\)
\(=\left(x^{98}-x^{97}+...-x+1\right)\left(x-2016\right)+2015\)
\(\Rightarrow f\left(2016\right)=2015\)
Vậy...
\(f\left(x\right)=x^{99}-2017^{x^{98}}+2017^{x^{97}}-...+2017x-1\)
\(f\left(2016\right)=2016^{99}-2017.2016^{98}+2017.2016^{97}-...+2017.2016-1\)
\(f\left(2016\right)=2016^{99}-\left(2016+1\right).2016^{98}+\left(2016+1\right).2016^{97}-...+\left(2016+1\right).2016-1\)
\(f\left(2016\right)=2016^{99}-2016^{99}-2016^{98}+2016^{98}+2016^{97}-2016^{97}-2016^{96}+...+2016^2+2016-1\)
\(f\left(2016\right)=2016-1\)
\(f\left(2016\right)=2015\)