tính giá trị biểu thức P =x^5+2x^4-2014x^3+x^2+2x-2013 khi x=√2015 -1
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Ta có: \(x=2013\Leftrightarrow x+1=2014\)
Thay vào ta được
\(C=x^4-\left(x+1\right)x^3+\left(x+1\right)x^2-\left(x+1\right)x+x+1\)
\(C=x^4-x^4-x^3+x^3+x^2-x^2-x+x+1\)
\(C=1\)
Vậy C = 1
x4-2014x3+2014x2-2014x+2014 = x4 - 2013x3 - x3 + 2013x2 + x2 +2013x + x + 2014
= x4 - 2013 (x3-x2+1) - (x3-x2+1) + 2014
= x4 -2014 (x3-x2+1) + 2014 = x4 - 2014 (x3-x2) = x4 - 2014 x2 (x-1) = x2 ( 20132 - 2014.2012) = x2 [20132 - (2013+1).(2013-1)]
= x2 = 20132
giúp tôi giải bài toán này giùm nhal bạn :/x+1/+/x+2/+/x+3/+...+/x+2013/=2014x
x = 2013 => x + 1 = 2014
Ta có:\(B=x^{2013}-2014x^{2012}+2014x^{2011}-2014x^{2010}+...+2014x-1\)
\(=x^{2013}-\left(x+1\right)x^{2012}+\left(x+1\right)x^{2011}-\left(x+1\right)x^{2010}+...+\left(x+1\right)x-1\)
\(=x^{2013}-x^{2013}-x^{2012}+x^{2012}+x^{2011}-x^{2011}-x^{2010}+...+x^2+x-1\)
\(=x-1\)
\(=2013-1\)
\(=2012\)
\(X=2013\Rightarrow2014=X+1\Rightarrow B=X^{2013}-\left(X+1\right)\times X^{2012}+...+\left(X+1\right)\times X-1\)\(X-1\)
\(\Rightarrow B=X^{2013}-X^{2013}-X^{2012}+...+X^2+X-1\)
\(\Rightarrow B=X-1\)\(=2013-1=2012\)
Ta thấy 2014=2013+1=x+1
B=x2013-2014x2012+2014x2011-2014x2011-2014x2010+.....-2014x2+2014x
B=x2013-(2013+1).x2012+(2013+1).x2011-(2013+1).x2011-(2013+1).x2010+....-(2013+1).x2+(2013+1).x
B=x2013-(x+1).x2012+(x+1).x2011-(x+1).x2011-(x+1).x2010+......-(x+1).x2+(x+1).x
B=x2013-x2013-x2012+x2012+x2011-x2012-x2011-x2011-x2010+....-x3-x2+x2+x
B=.....................(tự triệt tiêu tiếp)
x=\(\sqrt{\frac{2-\sqrt{3}}{2}}\) =\(\sqrt{\frac{4-2\sqrt{3}}{4}}=\frac{\sqrt{3}-1}{2}\)
\(\Rightarrow2x=\sqrt{3}-1\Rightarrow2x+1=\sqrt{3}\Rightarrow\left(2x+1\right)^2=3\Leftrightarrow4x^2+4x+1=3\Leftrightarrow4x^2+4x-2=0\Leftrightarrow2x^2+2x-1=0\)
nên đề bài = \(\left(x^3\left(2x^2+2x-1\right)+1\right)^{2013}+\frac{\left(x\left(2x^2+2x-1\right)-3\right)^{2013}}{x^2\left(2x^2+2x-1\right)-3^{2013}}\)
=\(\left(0+1\right)^{2013}+\frac{\left(0-3\right)^{2013}}{0-3^{2013}}=1+1=2\)
cho 2014=2013+1 thay vào ta có:\(B=x^{2013}-\left(2013+1\right)x^{2012}+\left(2013+1\right)x^{2011}-...-\left(2013+1\right)x^2+\left(2013+1\right)x-1\)
\(=x^{2013}-\left(x+1\right)x^{2012}+\left(x+1\right)x^{2011}-...-\left(x+1\right)x^2+\left(x+1\right)x-1\)
\(=x^{2013}-x^{2013}-x^{2012}+x^{2012}+x^{2011}-...-x^3-x^2+x^2+x-1\)
\(=x-1=2013-1=2012\)
i don't now
mong thông cảm !
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