chỉ cần lấy máy tính thôi nhé

a)8/7<7/8 b)9/5>5/8

Cách làm đây nhé

a) \(\dfrac{x}{5}=\dfrac{2}{5}\)

\(\Rightarrow5x=10\)

\(\Leftrightarrow x=2\)

Vậy x = 2

b) ĐKXĐ: \(x\ne0\)

 \(\dfrac{3}{-8}=\dfrac{6}{-x}\)

\(\Rightarrow-3x=-48\)

\(\Leftrightarrow x=16\)

Vậy x = 16

c) \(\dfrac{1}{9}=\dfrac{-2x}{10}\)

\(\Rightarrow-18x=10\)

\(\Leftrightarrow x=-\dfrac{5}{9}\)

Vậy \(x=-\dfrac{5}{9}\)

d) ĐKXĐ: \(x\ne0\)

 \(\dfrac{3}{x}-5=\dfrac{-9}{x}+2\)

\(\Leftrightarrow\dfrac{3-5x}{x}=\dfrac{-9+2x}{x}\)

\(\Rightarrow3-5x=-9+2x\)

\(\Leftrightarrow7x=12\)

\(\Leftrightarrow x=\dfrac{12}{7}\)

Vậy \(x=\dfrac{12}{7}\)

e) ĐKXĐ: \(x\ne0\)

 \(\dfrac{x}{-2}=\dfrac{-8}{x}\)

\(\Rightarrow x^2=16\)

\(\Leftrightarrow x=\pm4\)

Vậy \(x=\pm4\)

a) Ta có: \(\dfrac{x}{5}=\dfrac{2}{5}\)

\(\Leftrightarrow x=\dfrac{2\cdot5}{5}=2\)

Vậy: x=2

b) Ta có: \(\dfrac{3}{-8}=\dfrac{6}{-x}\)

\(\Leftrightarrow-x=\dfrac{6\cdot\left(-8\right)}{3}=-16\)

hay x=16

Vậy: x=16

Đề yêu cầu gì vậy em?

đây là so sánh hay quy đồng v 

\(\dfrac{3}{5}v\text{à}\dfrac{7}{3}\\ MSC:15\\ \dfrac{3}{5}=\dfrac{3\times3}{5\times3}=\dfrac{9}{15};\dfrac{7}{3}=\dfrac{7\times5}{5\times3}=\dfrac{35}{15}\\ 9< 35\\ \Rightarrow\dfrac{3}{5}< \dfrac{7}{5}\\ \dfrac{9}{10}v\text{à}\dfrac{5}{4}\\MSC:20\\ \dfrac{9\times2}{10\times2}=\dfrac{18}{20};\dfrac{5}{4}=\dfrac{5\times5}{4\times5}=\dfrac{25}{20}\\ 18< 25\\ \Rightarrow\dfrac{9}{10}< \dfrac{5}{4}\\ \dfrac{2}{7}v\text{à}\dfrac{5}{4}\\ MSC:28\\ \dfrac{2}{7}=\dfrac{2\times4}{7\times4}=\dfrac{8}{28};\dfrac{5}{4}=\dfrac{5\times7}{4\times7}=\dfrac{35}{28}\\ 8< 35\\ \dfrac{2}{7}< \dfrac{5}{4}\\ \dfrac{8}{9}v\text{à}\dfrac{11}{6}\\ MSC:18\\ \dfrac{8\times2}{9\times2}=\dfrac{16}{18};\dfrac{11}{6}=\dfrac{11\times3}{6\times3}=\dfrac{33}{18}\\ 16< 33\\ \Rightarrow\dfrac{8}{9}< \dfrac{11}{6}\)

Quy đồng hả ?

\(\dfrac{3}{5}và\dfrac{7}{3}=\dfrac{3}{5}=\dfrac{3\times3}{5\times3}=\dfrac{9}{15};\dfrac{7}{3}=\dfrac{7\times5}{3\times5}=\dfrac{35}{15}\)

\(\dfrac{9}{10}và\dfrac{5}{4}=\dfrac{9}{10}=\dfrac{9\times2}{10\times2}=\dfrac{18}{20};\dfrac{5}{4}=\dfrac{5\times5}{4\times5}=\dfrac{25}{20}\)

\(\dfrac{2}{7}và\dfrac{5}{4}=\dfrac{2}{7}=\dfrac{2\times4}{7\times4}=\dfrac{8}{28};\dfrac{5}{4}=\dfrac{5\times7}{4\times7}=\dfrac{35}{28}\)

\(\dfrac{8}{9}và\dfrac{11}{6}=\dfrac{8}{9}=\dfrac{8\times2}{9\times2}=\dfrac{16}{18};\dfrac{11}{6}=\dfrac{11\times3}{6\times3}=\dfrac{33}{18}\)

\(\dfrac{6}{5}và\dfrac{13}{8}=\dfrac{6\times8}{5\times8}=\dfrac{48}{40};\dfrac{13}{8}=\dfrac{13\times5}{8\times5}=\dfrac{65}{40}\)

\(\dfrac{4}{5}và\dfrac{3}{2}=\dfrac{4}{5}=\dfrac{4\times2}{5\times2}=\dfrac{8}{10};\dfrac{3}{2}=\dfrac{3\times5}{2\times5}=\dfrac{15}{10}\)

\(\dfrac{5}{12}và\dfrac{7}{8}=\dfrac{5}{12}=\dfrac{5\times2}{12\times2}=\dfrac{10}{24};\dfrac{7}{8}=\dfrac{7\times3}{8\times3}=\dfrac{21}{24}\)

\(\dfrac{11}{4}và\dfrac{13}{6}=\dfrac{11}{4}=\dfrac{11\times3}{4\times3}=\dfrac{33}{12};\dfrac{13}{6}=\dfrac{13\times2}{6\times2}=\dfrac{26}{12}\)

1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 = 45 + 10 = 55

* Hok tốt !

=(1+9)+(2+8)+(3+7)+(4+6)+10+5

=10+10+10+10+10+5

=10.5+5

=50+5

=55

1+2+3+4+5+6+7+8+9+10=(1+10)+(2+9)+(3+8)+(4+7)+(5+6)=11+11+11+11+11=11.5=55

bài 2

làm câu B;C nha

B)

\(27^3=\left(3^3\right)^3=3^9\)

\(9^5=\left(3^2\right)^5=3^{10}\)

vì \(10>9\)

\(=>9^5>27^3\)

C)

\(\left(\frac{1}{8}\right)^6=\left(\frac{1}{2^3}\right)^6=\frac{1^6}{2^{18}}=\frac{1}{2^{18}}\)

\(\left(\frac{1}{32}\right)^4=\left(\frac{1}{2^5}\right)^4=\frac{1^4}{2^{20}}=\frac{1}{2^{20}}\)

vì \(2^{18}< 2^{20}\)

\(=>\frac{1}{2^{18}}>\frac{1}{2^{20}}\)

\(=>\left(\frac{1}{8}\right)^6>\left(\frac{1}{32}\right)^4\)

\(\text{A.}\frac{32^3.9^5}{8^3.6^6}=\frac{\left(2^5\right)^3.\left(3^2\right)^5}{\left(2^3\right)^3.\left(2.3\right)^6}=\frac{2^{15}.3^{10}}{2^9.2^6.3^6}=\frac{3^{10}}{3^6}=3^4=81\)

\(\text{B.}\frac{\left(5^5-5^4\right)^3}{50^6}=\frac{2500^3}{50^6}=\frac{\left(50^2\right)^3}{50^6}=\frac{50^6}{50^6}=1\)

Bài 2:

\(\text{A.Ta có:}\)

\(5^6=\left(5^3\right)^2=125^2\)

\(\left(-2\right)^{14}=2^{14}=\left(2^7\right)^2=128^2\)

Vì \(125< 128\)

\(\Rightarrow125^2< 128^2\)

\(\Rightarrow5^6< \left(-2\right)^{14}\)

\(\text{B.Ta có:}\)

\(9^5=\left(3^2\right)^5=3^{10}\)

\(27^3=\left(3^3\right)^3=3^9\)

Vì \(9< 10\)

\(\Rightarrow3^9< 3^{10}\)

\(\Rightarrow27^3< 9^5\)

\(\text{C.Ta có:}\)

\(\left(\frac{1}{8}\right)^6=\left[\left(\frac{1}{2}\right)^3\right]^6=\left(\frac{1}{2}\right)^{18}\)

\(\left(\frac{1}{32}\right)^4=\left[\left(\frac{1}{2}\right)^5\right]^4=\left(\frac{1}{2}\right)^{20}\)

Vì \(18< 20\)

\(\Rightarrow\left(\frac{1}{2}\right)^{18}< \left(\frac{1}{2}\right)^{20}\)

\(\Rightarrow\left(\frac{1}{8}\right)^6< \left(\frac{1}{32}\right)^4\)