\(\frac{3}{1.4}+\frac{3}{2.6}+\frac{3}{3.8}+...+\frac{1}{2012.1342}\)

\(=\frac{3}{1.4}+\frac{3}{2.6}+\frac{3}{3.8}+...+\frac{3}{2012.4026}\)

\(=\frac{6}{2.4}+\frac{6}{4.6}+\frac{6}{4.8}+...+\frac{6}{4024.4026}\)

\(=3\cdot\left(\frac{2}{2.4}+\frac{2}{4.6}+\frac{2}{6.8}+...+\frac{2}{4024.4026}\right)\)

\(=3\cdot\left(\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+\frac{1}{6}-\frac{1}{8}+...+\frac{1}{4024}-\frac{1}{4026}\right)\)

\(=3\cdot\left(\frac{1}{2}-\frac{1}{4026}\right)\)

\(=3\cdot\frac{1}{2}-3\cdot\frac{1}{4026}\)

\(=1,5-\frac{3}{4026}< 1,5\)

1,5 = 3/2

-1,6 = -8/5

3,8 = 19/5

\(\frac{x\times0,75+2,4}{3,8-0,8}\)

\(=\frac{x\times0,75+2,4}{3}\)

\(x\times0,75=3-2,4\)

\(x\times0,75=0,6\)

\(x=0,6\div0,75\)

\(x=0,8\)

tao ko biết

\(3.8^x-2.2^{3x}-16=0\)

Đề như thế này ạ

\(3.8^x-2.2^{3x}-16=0\)

\(\Leftrightarrow3.\left(2^3\right)^x-2.2^{3x}=16\)

\(\Leftrightarrow3.2^{3x}-2^{3x}=16\)

\(\Leftrightarrow2^{3x}\left(3-1\right)=16\)

\(\Leftrightarrow2^{3x}.2=16\)

\(\Leftrightarrow2^{3x+1}=2^4\)

\(\Leftrightarrow3x+1=4\)

\(\Leftrightarrow x=1\)

Vậy ....

x*0,75+2.4/3.8-0.8=6.4

x*0.75+2.4/3=6.4

x*0.75+2.4/3=19.2/3

gach mau so ta co

x*0.75+2.4=19.2

x*0.75=19.2-2.4

x*0.75=16.8

x=16.8/0.75

x=22.4

bn vô đây Giúp tôi giải toán - Hỏi đáp, thảo luận về toán học - Học toán với OnlineMath

\(\frac{x}{y}=\frac{2}{5}\)\(\Rightarrow\)\(\frac{x}{2}=\frac{y}{5}\)hay  \(\frac{0,2x}{0,4}=\frac{0,3y}{1,5}\)

Áp dụng tính chất dãy tỉ số bằng nhau ta có:

\(\frac{0,2x}{0,4}=\frac{0,3y}{1,5}=\frac{0,2x+0,3y}{0,4+1,5}=\frac{3,8}{1,9}=2\)

suy ra:  \(\frac{0,2x}{0,4}=2\)\(\Rightarrow\)\(x=4\)

              \(\frac{0,3y}{1,5}=2\) \(\Rightarrow\)\(y=10\)