Ta có:  \(\left(x-\frac{1}{5}\right)^{2020}\ge0\forall x\)

         \(\left(y+0.4\right)^{2000}\ge0\forall y\)

        \(\left(z-3\right)^6\ge0\forall z\)

=> \(\left(x-\frac{1}{5}\right)^{2020}+\left(y+0.4\right)^{2000}+\left(z-3\right)^6\ge0\forall x,y,z\)

Dấu "=" xảy ra khi: \(\hept{\begin{cases}x-\frac{1}{5}=0\\y+0.4=0\\z-3=0\end{cases}}\) => \(\hept{\begin{cases}x=\frac{1}{5}\\y=0\\z=3\end{cases}}\)

vậy ...

a) \(\frac{x}{1}=\frac{y}{3}=\frac{4z}{15}=\frac{6x+7y+8z}{1.6+3.7+15.2}=\frac{456}{57}=8\)

x=8

y=24

z=30

\(3x=y\)=>  \(\frac{x}{1}=\frac{y}{3}\)

hay  \(\frac{x}{4}=\frac{y}{12}\)

\(5y=4z\)=>  \(\frac{y}{4}=\frac{z}{5}\)

hay  \(\frac{y}{12}=\frac{z}{15}\)

suy ra:   \(\frac{x}{4}=\frac{y}{12}=\frac{z}{15}\)

đến đây bạn ADTCDTSBN nhé

Ta có: 3x=y⇒x1=y3⇒x4=y123x=y⇒x1=y3⇒x4=y12

5y=4z⇒y4=z5⇒y12=z155y=4z⇒y4=z5⇒y12=z15

⇒x4=y12=z15⇒x4=y12=z15

Áp dụng tính chất dãy tỉ số bằng nhau ta có:
x4=y12=z15=6x24=7y84=8z120=6x+7y+8z24+84+120=456228=2x4=y12=z15=6x24=7y84=8z120=6x+7y+8z24+84+120=456/228=2

+) x4=2⇒x=8x4=2⇒x=8

+) y12=2⇒y=24y12=2⇒y=24

+) z15=2⇒z=30z15=2⇒z=30

Vậy bộ số (x;y;z)(x;y;z) là (8;24;30)

chtt có thật sao mk  ko biết đấy!!!!!!!!!!!!!!!!!! 

Vì (x-1/5)²⁰⁰⁴ ≥ 0 ; (y+0.4)¹⁰⁰ ≥ 0 ; (z-3)⁶⁷⁸ ≥ 0 với mọi x,y,z

Để (x-1/5)²⁰⁰⁴+(y+0.4)¹⁰⁰+(z-3)⁶⁷⁸=0 <=> (x-1/5)²⁰⁰⁴ = 0 ; (y+0.4)¹⁰⁰ = 0 ; (z-3)⁶⁷⁸ = 0

=> x-1/5 = 0 ; y+0.4=0 ; z-3=0

=> x=1/5 ; y=-0.4 ; z=3

Bn chấp nhận kết bn mình nha

f(1)=5.1-1=5-1=4;f(4)=5.4-1=20-1=19;f(1,2)=5.1,2-1=6-1=5;f(0,4)=5.0,4-1=2-1=1

Ta có: \(0,\left(3\right)+\frac{31}{3}+0,4\left(2\right)=\frac{3}{9}+\frac{31}{3}+\frac{42-4}{90}=\frac{1}{3}+\frac{31}{3}+\frac{19}{45}=\frac{32}{3}+\frac{19}{45}=\frac{499}{45}.\)

\(\frac{4}{9}+0,\left(13\right)=\frac{4}{9}+\frac{13}{99}=\frac{44}{99}+\frac{13}{99}=\frac{57}{99}=\frac{19}{33}\)

\(0,\left(37\right).x\Rightarrow\frac{37}{99}.x=1\)

\(\Rightarrow x=1:\frac{37}{99}=\frac{99}{37}\)

\(0,\left(26\right).x=1,2\left(31\right)\)

\(\Rightarrow\frac{26}{99}.x=\frac{1219}{990}\)

\(\Rightarrow x=\frac{1219}{990}:\frac{26}{99}=\frac{1219}{260}\)