Tính B=2014X100+2014X99+2014X98+....+2014X2+2014 tại X=2015
Tính bằng cách thuận tiện nhất:2014x4+2x3x1007+2014x2+2014
\(=2014\left(4+3+2+1\right)=20140\)
( 1+2+3+4+5+6+7.....+108+109)x(2014x3-2014x2-2014)
=(1+2+3+4+5+6+7+.....+108+109)x(2014x(3-2-1))
=(1+2+3+4+5+6+7+.....+108+109)x(2014x0)
=Ax0
=0
( 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 ) x ( 2014 x 3 - 2014 x 2 - 2014 )
= ( 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 ) x 0
= 0
0 nhân với số nào cũng bằng 0
Tính giá trị của biểu thức
x^2016 - 2015*x^2015-2015*x^2014-....-2015*x+1 tại x=2016
Cho \(M=\frac{X\left(yz-x^2\right)+y\left(zx-y^2\right)+z\left(xy-z^2\right)}{\left(x-y\right)^2+\left(y-z\right)^2+\left(z-x\right)^2}\)
Tính giá trị của M tại \(x=2014^{2015}-20142015;y=20142015-2015^{2014};z=2015^{2014}-2014^{2015}\)
Cho \(M=\frac{x\left(yz-x^2\right)+y\left(zx-y^2\right)+z\left(xy-z^2\right)}{\left(x-y\right)^2+\left(y-z\right)^2+\left(z-x\right)^2}\)
Tính giá trị của M tại \(x=2014^{2015}-20142015;y=20142015-2015^{2014};z=2015^{2014}-2014^{2015}\)
Ta có:
\(M=\frac{x\left(yz-x^2\right)+y\left(zx-y^2\right)+z\left(xy-z^2\right)}{\left(x-y\right)^2+\left(y-z\right)^2+\left(z-x\right)^2}=\frac{xyz-x^3+xyz-y^3+xyz-z^3}{\left(x-y\right)^2+\left(y-z\right)^2+\left(z-x\right)^2}=\frac{3xyz-x^3-y^3-z^3}{\left(x-y\right)^2+\left(y-z\right)^2+\left(z-x\right)^2}\)
\(-M=\frac{x^3+y^3+z^3-3xyz}{\left(x-y\right)^2+\left(y-z\right)^2+\left(z-x\right)^2}\)
Xét đẳng thức phụ:
\(a^3+b^3+c^3-3abc=\left(a+b\right)^3-3ab\left(a+b\right)+c^3-3abc=\left[\left(a +b\right)^3+c^3\right]-3ab\left(a+b+c\right)\)\(=\left(a+b+c\right)\left(\left(a+b\right)^2-c\left(a+b\right)+c^2\right)-ab\left(a+b+c\right)\)
\(=\left(a+b+c\right)\left[\left(a+b\right)^2-c\left(a+b\right)+c^2-ab\right]=\left(a+b+c\right)\left(a^2+b^2+c^2-ab-bc-ac\right)\)
\(=\frac{1}{2}\left(a+b+c\right)\left(2a^2+2b^2+2c^2-2ab-abc-ac\right)\)
\(=\frac{1}{2}\left(a+b+c\right)\left[\left(a-b\right)^2+\left(b-c\right)^2+\left(c-a\right)^2\right]\)
Thay vào -M ta có:
\(-M=\frac{\frac{1}{2}\left(x+y+z\right)\left[\left(x-y\right)^2+\left(y-z\right)^2+\left(z-x\right)^2\right]}{\left(x-y\right)^2+\left(y-z\right)^2+\left(z-x\right)^2}=\frac{1}{2}\left(x+y+z\right)\Rightarrow M=-\frac{1}{2}\left(x+y+z\right)\)
Giờ thay: \(x=2014^{2015}-20142015;y=20142015-2015^{2014};z=2015^{2014}-2014^{2015}\)
Ta có:
\(M=-\frac{1}{2}\left(2014^{2015}-20142015+20142015-2015^{2014}+2015^{2014}-2014^{2015}\right)=0\)
Tính giá trị của biểu thức
x^2016 + x^2015+ x^2014+...+x+1 tại x =2
\(A=1+2+...+2^{2015}+2^{2016}\)
\(2A=2+2^2+...+2^{2016}+2^{2017}\)
\(2A-A=\left(2+2^2+...+2^{2017}\right)-\left(1+2+...+2^{2016}\right)\)
\(A=2^{2017}-1\)
\(B=2^{2016}+2^{2015}+2^{2014}+...+2+1\)
\(\Rightarrow B=1+2+...+2^{2014}+2^{2015}+2^{2016}\)
\(\Rightarrow2B=2+2^2+...+2^{2015}+2^{2016}+2^{2017}\)
\(\Rightarrow2B-B=2^{2017}-1\Rightarrow B=2^{2017}-1\)
Đặt C=1+2+....+22015+22016
=> 2C=2+22+23+....+22017
=> 2C-C=22017--1
=>C = 22017--1
Cho a^2014 + b^2014 + c^2014 =1 và a^2015 + b^2015 + c^2015 =1. Tính tổng A= a^2013+b^2014+c^2015
a2014+b2014+c2014=1
a2015+b2015+c2015=1
=>a2014+b2014+c2014=a2015+b2015+c2015=1
=>a=b=1
=>A=3
Cho x,y thỏa mãn (x + căn 2014+y^2)(y + căn 2014+x^2)=2014 . tính x^2015 + y^2015
Tính 2014 x 2015 + 2016 / 2016 x 2015 - 2014
\(\frac{2014.2015+2016}{2015.2016-2014}=\frac{2014.2015+2016}{2015.2014+4030-2014}=\frac{2014.2015+2016}{2014.2015+2016}=1\)