cho \(x+y+z=0\) và x2+y2+z2 = 1
khí đó giá trị của biểu thức M= \(2\left(x^4+y^4+z^4\right)là\)
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HT
11 tháng 4 2021
\(\Delta'=4-5=-1\Rightarrow\left[{}\begin{matrix}z_1=2+i\\z_2=2-i\end{matrix}\right.\)
\(\Rightarrow\left(z_1-1\right)^{2019}+\left(z_2-1\right)^{2019}=\left(i+1\right)^{2019}+\left(i-1\right)^{2019}\)
\(=\left(i+1\right)\left[\left(i+1\right)^2\right]^{1009}+\left(i-1\right)\left[\left(i-1\right)^2\right]^{1009}\)
\(=\left(i+1\right)\left(2i\right)^{1009}+\left(1-i\right)\left(-2i\right)^{1009}=\left(2i\right)^{1009}\left(i+1+i-1\right)=\left(2i\right)^{1009}.2i=\left(2i\right)^{1010}=-2^{1010}\)
=>D
P/s: Sry nó bị trôi thông báo nên toi ko để ý
9 tháng 8 2018
Ta có:\(P=x^3\left(z-y^2\right)+y^3x-y^3z^2+z^3y-z^3x^2+x^2y^2z^2-xyz\)
\(\Rightarrow P=x^3\left(z-y^2\right)+x^2y^2z^2-x^2z^3-\left(y^3z^2-z^3y\right)+y^3x-xyz\)
\(\Rightarrow P=x^3\left(z-y^2\right)+x^2z^2\left(y^2-z\right)-yz^2\left(y^2-z\right)+xy\left(y^2-z\right)\)
\(\Rightarrow P=\left(y^2-z\right)\left(x^2z^2-x^3-yz^2+xy\right)\)
\(\Rightarrow P=\left(y^2-z\right)\left(x^2z^2-x^3+xy-yz^2\right)\)
\(\Rightarrow P=\left(y^2-z\right)\left(x^2\left(z^2-x\right)+y\left(x-z^2\right)\right)\)
\(\Rightarrow P=\left(y^2-z\right)\left(x^2\left(z^2-x\right)-y\left(z^2-x\right)\right)\)
\(\Rightarrow P=\left(y^2-z\right)\left(z^2-x\right)\left(x^2-y\right)\)
\(\Rightarrow P=abc\)
Vì a, b, c là hằng số nên P có giá trị không phụ thuộc vào x, y, z
9 tháng 6 2021
a, ĐKXĐ: x≠±2
A=\(\left(\dfrac{x}{x^2-4}+\dfrac{2}{2-x}+\dfrac{1}{x+2}\right)\left(x-2+\dfrac{10-x^2}{x+2}\right)\)
A=\(\left(\dfrac{x}{x^2-4}-\dfrac{2x+4}{x^2-4}+\dfrac{x-2}{x^2-4}\right)\left(\dfrac{x^2+2x}{x+2}-\dfrac{2x+4}{x+2}+\dfrac{10-x^2}{x+2}\right)\)
A=\(\left(\dfrac{-6}{x^2-4}\right)\left(\dfrac{6}{x+2}\right)\)
A=\(\dfrac{-36}{\left(x-2\right)\left(x+2\right)^2}\)
b, |x|=\(\dfrac{1}{2}\)
TH1z: x≥0 ⇔ x=\(\dfrac{1}{2}\) (TMĐKXĐ)
TH2: x<0 ⇔ x=\(\dfrac{-1}{2}\) (TMĐXĐ)
Thay \(\dfrac{1}{2}\), \(\dfrac{-1}{2}\) vào A ta có:
\(\dfrac{-36}{\left(\dfrac{1}{2}-2\right)\left(\dfrac{1}{2}+2\right)^2}\)=\(\dfrac{96}{25}\)
\(\dfrac{-36}{\left(\dfrac{-1}{2}-2\right)\left(\dfrac{-1}{2}+2\right)^2}\)=\(\dfrac{32}{5}\)
c, A<0 ⇔ \(\dfrac{-36}{\left(x-2\right)\left(x+2\right)^2}\) ⇔ (x-2)(x+2)2 < 0
⇔ {x-2>0 ⇔ {x>2
[ [
{x+2<0 {x<2
⇔ {x-2<0 ⇔ {x<2
[ [
{x+2>0 {x>2
⇔ x<2
Vậy x<2 (trừ -2)
\(\left\{{}\begin{matrix}x+y+z=0\\x^2+y^2+z^2=1\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}x^2+y^2+z^2+2\left(xy+xz+yz\right)=0\\xy+xz+yz=-\dfrac{1}{2}\end{matrix}\right.\) \(\left\{{}\begin{matrix}x^4+y^4+z^4+2\left[\left(xy\right)^2+\left(xz\right)^2+\left(yz\right)^2\right]=1\\xy+xz+yz=\dfrac{-1}{2}\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}2\left(x^4+y^4+z^4\right)=2-4\left[\left(xy\right)^2+\left(xz\right)^2+\left(yz\right)^2\right]\\\left(xy\right)^2+\left(xz\right)^2+\left(yz\right)^2+2\left[xyz\left(x+y+z\right)\right]=\dfrac{1}{4}\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}2\left(x^4+y^4+z^4\right)=2-4.\dfrac{1}{4}\\\left(xy\right)^2+\left(xz\right)^2+\left(yz\right)^2=\dfrac{1}{4}\end{matrix}\right.\) \(\Rightarrow2\left(x^4+y^4+z^4\right)=2-1=1\)