1. 21x=11

2.-0,25

3.\(\frac{-1}{5}\)

4. 14,4m

5. 4 điểm

1) 11

2) -0,25

3) 1/5

4) 9,6

5) 4 

nnhanh len giumm

ban kia lam dung roi do 

k tui nha

thanks

2/3+1/3:x=-1

      1/3:x=-1-2/3

      1/3:x=-5/3

           x =1/3:(-5/3)

           x = -1/5

-1:5=-0,1 

Vậy x = -0,2

x=-1. 1/3:x=-1+2/3     1/3:x=-1/3     x=-1/3:1/3   Suy ra x=-1

ta có :

\(\frac{3}{4}+\frac{1}{4}:x=-3\Rightarrow\frac{1}{4}:x=\left(-3\right)-\frac{3}{4}\Rightarrow\frac{1}{4}:x=\frac{-15}{4}\)

\(x=\frac{1}{4}:\frac{-15}{4}=\frac{-1}{15}=0,0\left(6\right)\)

3/4+1/4:x=-3 \(\Rightarrow\)1/4:x=-3-3/4=-15/4\(\Rightarrow\)x=1/4:(-15/4)=-1/15\(\Rightarrow\)3x=-1/15.3=-1/5

\(\frac{3}{4}+\frac{1}{4}:x=-3\)

\(\Rightarrow\frac{1}{4}:x=-3-\frac{3}{4}=-\frac{15}{4}\)

\(\Rightarrow x=\frac{1}{4}:\left(-\frac{15}{4}\right)=-\frac{1}{15}\)

\(\Rightarrow3.x=3.\left(-\frac{1}{15}\right)=-\frac{1}{5}=-0,2\)

\(A=2^0+2^1+2^2+...+2^{21}\)

\(2A=2^1+2^2+2^3+...+2^{22}\)

\(2A-A=\left(2^1+2^2+2^3+...+2^{22}\right)-\left(2^0+2^1+2^2+...+2^{21}\right)\)

\(A=2^{22}-1\)

\(2^{22}-1=2^{2n}-1\)

\(2^{2\times11}-1=2^{2n}-1\)

n = 11

câu 1: 11

câu 2: 0,125

câu 3: -1;0;1

câu 4: -2,5

0,52

k cho mình nhé

t=(1-1/4)x(1-1/9)x(1-1/16)x.......(1-1/157)x(1-1/625)

= 3/4 x 8/9 x 15/16 x ... x 156/157 x 624/625

=  (3 x 2 x4 x 3 x 5 x... x 23x25 x 24 x26) / (2x2 x 3x3 x 4x4 x ...x 24x24 x 25x25)

(giản ước tử số và mẫu số ta được)

= (1x26) / (2x25)

= 13/25

ĐS: 13/25

x = 1/8 = 0,125

mk thi rùi 300đ

x= 0,125