tim x biet x(x-2005)-2010x+2009+2010
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\(x.\left(x-2009\right)-2010x+2009.2010=0\)
\(x.\left(x-2009\right)-2010\left(x-2009\right)=0\)
\(\left(x-2009\right)\left(x-2010\right)=0\)
\(\Rightarrow\orbr{\begin{cases}x-2009=0\\x-2010=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=2009\\x=2010\end{cases}}}\)
Vậy \(\orbr{\begin{cases}x=2009\\x=2010\end{cases}}\)
Thay 2010 = x + 1 vào P ( x ),ta có :
\(^{x^{10}-\left(x+1\right)x^9+\left(x+1\right)x^8-\left(x+1\right)x^7+...+\left(x+1\right)x^2-\left(x+1\right)x-1}\)
= x10 - x10 - x9 + x9 + x8 - x8 - x7 + ... + x3 + x2 - x2 + x - 1
= x + 1
= 2009 + 1
= 2010
Thay 2010 = x+ 1 vào P( x) ,có :
\(x^{10}-\left(x+1\right)x^9+\left(x+1\right)x^8-\left(x+1\right)x^7+...+\left(x+1\right)x^2-\left(x+1\right)x-1\)
= \(x^{10}-x^{10}-x^9+x^9+x^8-x^8-x^7+...+x^3+x^2-x^2+x-1\)
= x+1
= 2009 + 1
= 2010
Ta có: x = 2011 \(\Rightarrow\) 2010 = x - 1
\(A=x^{2011}-2010x^{2010}-2010x^{2009}-...-2010x+1\)
\(=x^{2011}-\left(x-1\right)x^{2010}-\left(x-1\right)x^{2009}-...-\left(x-1\right)x+1\)
\(=x^{2011}-\left(x-1\right)x^{2010}-\left(x-1\right)x^{2009}-...-\left(x-1\right)x+1\)
\(=x^{2011}-x^{2011}+x^{2010}-x^{2010}+x^{2009}-...-x^2+x+1\)
\(=x+1\)
\(=2011+1\)
\(=2012.\)
x=2011
=> 2010= x-1
A = x^2011- (x-1) x^2010- (x-1).x^2009-.....- (x-1).x+1
= x^2011-x^2011+x^2010- x^2010+x^2009..x^2.-x^2+x+1
= x+1
=(x-1)+2= 2010+2=2012
\(\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{x.\left(x+1\right)}=\frac{2005}{2010}\)
\(\Leftrightarrow1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{x}-\frac{1}{x+1}=\frac{401}{402}\)
\(\Leftrightarrow1-\frac{1}{x+1}=\frac{401}{402}\)
\(\Leftrightarrow\frac{1}{x+1}=1-\frac{401}{402}\)
\(\Leftrightarrow\frac{1}{x+1}=\frac{1}{402}\)
\(\Leftrightarrow x+1=402\Rightarrow x=401\)
tim x
x(x-2015)-2010x+2009*2010=0