Nhờ mn làm giùm mình vs nhé c.ơn nhìu ạ

a) Đặt A=1/2 + 1/4 + 1/8 +...+ 1/256 + 1/512

\(A=\frac{1}{2}+\frac{1}{2^2}+...+\frac{1}{2^9}\)

\(2A=1+\frac{1}{2}+...+\frac{1}{2^8}\)

\(2A-A=\left(1+\frac{1}{2}+...+\frac{1}{2^8}\right)-\left(\frac{1}{2}+\frac{1}{2^2}+...+\frac{1}{2^9}\right)\)

\(A=1-\frac{1}{2^9}\)

b)\(\frac{a}{b}+\frac{4}{6}+\frac{2}{10}=\frac{3}{2}\)

\(\Rightarrow\frac{a}{b}+\frac{13}{15}=\frac{3}{2}\)

\(\Rightarrow\frac{a}{b}=\frac{19}{30}\)

\(\frac{4}{5}:\frac{a}{b}-\frac{6}{5}=\frac{3}{10}\)

\(\Rightarrow\frac{4}{5}:\frac{a}{b}=\frac{3}{2}\)

\(\Rightarrow\frac{a}{b}=\frac{8}{15}\)

a) \(\frac{3}{-4}=\frac{-3}{4};\frac{-1}{-4}=\frac{1}{4}\)

Vì - 3 < 1 nên \(\frac{-3}{4}< \frac{1}{4}\)

hay \(\frac{3}{-4}< \frac{-1}{-4}\)

Quy đồng mẫu ta được:

15/17=15.27/17.27=405/459

25/27=25.17/27.27=425/459

⇒405/459<425/459⇒15/17<25/27

câu 2 là so sánh nhé các bn các bn giúp mk nhé

2:

a: =4+3/8+5+2/3

=9+3/8+2/3

=216/24+9/24+16/24

=216/24+25/24

=241/24

b; =2+3/8+1+1/4+3+6/7

=6+3/8+1/4+6/7

=6+5/8+6/7

=419/56

c: \(=2+\dfrac{3}{8}-1-\dfrac{1}{4}+5+\dfrac{1}{3}\)

=6+3/8-1/4+1/3

=6+1/8+1/3

=6+11/24

=155/24

d: \(=3+\dfrac{5}{6}+6\cdot\dfrac{13}{6}\)

=3+13+5/6

=16+5/6

=101/6

e: =3+1/2+4+5/7-5-5/14

=3+4-5+1/2+5/7-5/14

=2+7/14+10/14-5/14

=2+12/14

=2+6/7=20/7

f: =9/2+1/2:11/2

=9/2+1/11

=99/22+2/22=101/22

a. \(A=\dfrac{1}{2}\cdot\dfrac{2}{3}+\dfrac{5}{10}\) \(B=\dfrac{7}{8}-\dfrac{1}{4}\cdot\dfrac{3}{2}\)

\(=\dfrac{1}{3}+\dfrac{1}{2}\) \(=\dfrac{7}{8}-\dfrac{3}{8}\\ =\dfrac{1}{2}\)

\(\Rightarrow A>B\)

b. \(C=\dfrac{2}{3}\cdot\dfrac{4}{5}+\dfrac{8}{15}-\dfrac{1}{15}\)

\(=\dfrac{8}{15}+\dfrac{7}{15}\\ =\dfrac{15}{15}\\ =1\)

\(D=\dfrac{1}{2}\cdot\dfrac{5}{6}+\dfrac{2}{3}\cdot\dfrac{3}{4}\)

\(=\dfrac{5}{12}+\dfrac{6}{12}\\ =\dfrac{11}{12}\)

\(\Rightarrow C>D\)

bài 2: n=6

KO AI TRẢ LỜI THẾ MH TRẢ LỜI LUN !

\(a,4^{72}v\text{à}8^{48}\)

TA CÓ:\(4^{72}=\left(2^2\right)^{72}=2^{144}\)

\(8^{48}=\left(2^3\right)^{48}=2^{144}\)

\(\Rightarrow4^{72}=8^{48}\)

\(b,5^{127}v\text{à}2^{254}\)

TA CÓ:\(2^{252}2^{2\times127}=\left(2^2\right)^{127}=4^{127}\)

\(5^{127}>4^{127}\left(v\text{ì5>4}\right)\)\(5^{127}>4^{127}\left(v\text{ì}5>4\right)\)

\(\Rightarrow5^{127}>2^{254}\)

a) Ta có : 4⁷² = 4^3.24 = (4³)²⁴ = 64²⁴

                8⁴⁸ = 8^2.24 = (8²)²⁴ = 64²⁴

Ta thấy : 64²⁴ = 64²⁴ => 4⁷² = 8⁴⁸

b) Ta có : 2²⁵⁴ = 2^2.127 = (2²)¹²⁷ = 4¹²⁷

Vì 5 > 4 => 5¹²⁷ > 2²⁵⁴

BÀI 1

a,  \(5\times\frac{-7}{10}=\frac{-35}{10}=\frac{-7}{2}\)

b,  \(\frac{4}{5}\times\frac{-7}{10}=\frac{-28}{50}=\frac{-14}{25}\)

c,  \(\frac{4}{9}+\frac{4}{3}\times\frac{16}{4}=\frac{4}{9}+\frac{16}{3}=\frac{52}{9}\)

d,  \(\frac{11}{22}-\frac{3}{9}\times\frac{14}{21}=\frac{11}{22}-\frac{2}{9}=\frac{55}{198}=\frac{5}{18}\)  

BÀI 2

\(A=\frac{6}{13}\times\frac{5}{7}+\frac{6}{13}\times\frac{2}{7}+\frac{17}{13}\)

\(A=\frac{30}{91}+\frac{12}{91}+\frac{17}{13}\)

\(A=\frac{30}{91}+\frac{12}{91}+\frac{119}{91}\)

\(A=\frac{161}{91}=\frac{23}{13}\)

\(B=\frac{11}{15}\times\frac{4}{11}+\frac{11}{15}\times\frac{5}{11}+\frac{11}{15}\times\frac{2}{11}\)

\(B=\frac{4}{15}+\frac{1}{3}+\frac{2}{15}\)

\(B=\frac{11}{15}\)

\(C=\left(\frac{19}{64}-\frac{33}{22}+\frac{24}{51}\right)\times\left(\frac{1}{5}-\frac{1}{15}-\frac{2}{15}\right)\)

\(C=\frac{-797}{1088}\times0\)

\(C=0\)

\(D=\frac{8}{13}\times\frac{7}{12}+\frac{8}{13}\times\frac{5}{12}-\frac{1}{12}\)

\(D=\frac{14}{39}+\frac{10}{39}-\frac{1}{12}\)

\(D=\frac{83}{156}\)

bạn biết câu náy không (24 + 11) . {546 - [14 . (64 - 2^{3}3) : 2]} =