c)\(1-\left(x-\frac{1}{5}\right)^2=\frac{21}{25}\)

\(\Leftrightarrow\left(x-\frac{1}{5}\right)^2=\frac{4}{25}\)

\(\Leftrightarrow x-\frac{1}{5}=\frac{2}{5}\)

\(\Leftrightarrow x=\frac{3}{5}\)

d)\(\left|x+\frac{1}{3}\right|.3\frac{2}{5}=\frac{2}{5}\)

\(\Leftrightarrow\left|x+\frac{1}{3}\right|.\frac{17}{5}=\frac{2}{5}\)

\(\Leftrightarrow\left|x+\frac{1}{3}\right|=\frac{2}{17}\)

\(\Leftrightarrow\orbr{\begin{cases}x+\frac{1}{3}=\frac{2}{17}\\x+\frac{1}{3}=-\frac{2}{17}\end{cases}\Leftrightarrow\orbr{\begin{cases}x=-\frac{11}{51}\\x=-\frac{23}{51}\end{cases}}}\)

#H

1-(x-1/5)²=21/25

   (x-1/5)²=1-21/25

   (x-1/5)²=4/25

   (x-1/5)²=(2/5)²

       x-1/5=2/5

             x=2/5+1/5

             x=3/5

k nha

123.123

=15129

#H

123.123= 15129

ko chắc lắm nha

ai chên 10 k mình nha

 a) 3126+985

=4111

  958+3126

=4084

3126+985=4201

958+3126=4201

Thấy đúng k cho tui

 4x+5x-x=128

x(4+5-1)=128

x.8=128

x=16

\(\frac{x-1}{x+2}=\frac{x-2}{x+3}\)

\(\Leftrightarrow\left(x-1\right)\left(x+3\right)=\left(x+2\right)\left(x-2\right)\)

\(\Leftrightarrow x^2+2x-3=x^2-4\)

\(\Leftrightarrow2x-3=-4\)

\(\Leftrightarrow2x=-1\)

\(\Leftrightarrow x=\frac{-1}{2}\)

Vậy x = -1/2

Trả lời :

C1 : { 1 ; 2 ; 3 ; 4 }

C2 : { x ∈ N* | x ≤ 4 }

\(\text{#Hok tốt!}\)

Ta có A = 2A – A = 2( 1 + 2 + 2 2 + 2 3 + . . . + 2 50 ) – ( 1 + 2 + 2 2 + 2 3 + . . . + 2 50 )

=  2 + 4 + 2 3 + 2 4 + . . . + 2 51  – ( 1 + 2 + 2 2 + 2 3 + . . . + 2 50 )

= 6 + 2 3 + 2 4 + . . . + 2 51  – ( 7 + 2 3 + . . . + 2 50 ) =  2 51 - 1

Suy ra : A + 1 =  2 51

Vậy A+1 là một lũy thừa của 2

\(C=4+2^2+2^3+...+2^{2005}\)   

\(=2^2+2^2+2^3+...+2^{2005}\)   

\(=2^3+2^3+...+2^{2005}\)   

\(=2^4+...+2^{2005}\)   

\(=2^{2006}\)

|2 - x| + 2 = x

<=> |2 - x| =  x - 2 (1)

ĐK : \(x-2\ge0\Leftrightarrow x\ge2\)

Khi đó (1) <=> \(\orbr{\begin{cases}2-x=x-2\\2-x=2-x\end{cases}}\Leftrightarrow\orbr{\begin{cases}2x=4\\0x=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=2\\\forall x\ge2\end{cases}}\)

Vậy \(x\ge2\)

Với x > 2 bthuc <=> -( 2 - x ) + 2 = x <=> x - 2 = x - 2 ( luôn đúng ) (1)

Với x <= 2 bthuc <=> 2 - x + 2 = x <=> x = 2 (tm) (2)

Từ (1) và (2) => x >=2 

a)\(\frac{5}{27}-\frac{8}{9}+\frac{3}{5}+\frac{22}{27}-\frac{1}{9}\)

= \(\left(\frac{5}{27}+\frac{22}{27}\right)+\left(-\frac{8}{9}-\frac{1}{9}\right)+\frac{3}{5}\)

= \(\frac{27}{27}-\frac{9}{9}+\frac{3}{5}\)

= \(1-1+\frac{3}{5}=\frac{3}{5}\)

b) \(15\frac{2}{3}-\left(3+5\frac{2}{3}\right)\)

= \(15+\frac{2}{3}-3-5-\frac{2}{3}\)

= \(\left(15-3-5\right)+\left(\frac{2}{3}-\frac{2}{3}\right)\)

= \(7\)