![](https://rs.olm.vn/images/avt/0.png?1311)
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
a, 53 x 39 + 47 x 39 + 53 x 21- 47 x 21
= ( 53 + 47 ) x 39 + ( 53 - 47 ) x 21
= 100 x 39 + 6 x 21
= 3900 + 126
= 4026
Mấy phần khác bạn tự làm đi
![](https://rs.olm.vn/images/avt/0.png?1311)
a: \(=\left(\dfrac{3}{4}+\dfrac{1}{4}\right)+\left(\dfrac{18}{21}+\dfrac{3}{21}\right)+\dfrac{19}{32}+\dfrac{13}{32}=1+1+1=3\)
b: \(=35\cdot1.1\cdot25\cdot\left(7,5-7,5\right)=0\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\Rightarrow\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+\frac{1}{4\cdot5}+\frac{1}{5\cdot6}+\frac{1}{42}\cdot\frac{x}{3}=\frac{5}{21}\)
\(\Rightarrow\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{42}\cdot\frac{x}{3}=\frac{5}{21}\)
\(\Rightarrow\frac{1}{2}-\frac{1}{6}+\frac{1}{42}\cdot\frac{x}{3}=\frac{5}{21}\)
\(\Rightarrow\frac{1}{3}+\frac{1}{42}\cdot\frac{x}{3}=\frac{5}{21}\)
\(\Rightarrow\frac{1}{42}\cdot\frac{x}{3}=\frac{5}{21}-\frac{1}{3}\)
\(\Rightarrow\frac{1}{42}\cdot\frac{x}{3}=\frac{-2}{21}\)
\(\Rightarrow\frac{x}{3}=\frac{-2}{21}\div\frac{1}{42}\)
\(\Rightarrow\frac{x}{3}=-4\)
\(\Rightarrow\frac{x}{3}=\frac{-12}{3}\)
\(\Rightarrow x=-12\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Sửa đề: \(x\cdot0,25+5,42=24,42\)
=>\(x\cdot0,25=24,42-5,42=19\)
=>\(x=19:0,25=19\cdot4=76\)
![](https://rs.olm.vn/images/avt/0.png?1311)
b1:
a,\(\frac{3}{8}:\frac{5}{4}\)=\(\frac{3}{8}.\frac{4}{5}=\frac{12}{45}=\frac{4}{15}\)
b,\(\frac{4}{7}:\frac{2}{13}=\frac{4}{7}.\frac{13}{2}=\frac{26}{7}\)
b2:
a,25:0,1=250 25x10=250 42:0,01=4200 42x100=4200 72:0,1=720 83:0,01=8300
b,13:0,25=52 13x4=52 42:0,5=84 42x2=84 75:0,5=150 125:0,25=500
![](https://rs.olm.vn/images/avt/0.png?1311)