a: 13,7x18+82x10,5+3,2x80

=246,6+861+256

=1363,6

b: 9,83:1,25:8+10,23:40:0,25

\(=9,83:\frac54:8+10,23\times\frac{1}{40}\times\frac{1}{0,25}\)

\(=9,83\times\frac45\times\frac18+10,23\times\frac{1}{40}\times4\)

\(=9,83\times\frac{1}{10}+10,23\times\frac{1}{10}=\frac{1}{10}\times\left(9,83+10,23\right)=\frac{1}{10}\times20,06=2,006\)

c: \(12,5\times0,42\times0,8:0,7\)

\(=12,5\times0,8\times0,42:0,7\)

\(=10\times\frac{42}{100}:\frac{7}{10}=\frac{42}{10}\times\frac{10}{7}=\frac{42}{7}=6\)

d: \(12,3\times4,7+5,3\times12,3-1,4\times7,5+7,5\times5,4\)

\(=12,3\times\left(4,7+5,3\right)+7,5\times\left(5,4-1,4\right)\)

\(=12,3\times10+7,5\times4\)

=123+30

=153

Ta có: \(3^{x-1}+5\cdot3^{x}+4\cdot3^{x+1}=1404\)

=>\(3^{x-1}+5\cdot3\cdot3^{x-1}+4\cdot3^2\cdot3^{x-1}=1404\)

=>\(52\cdot3^{x-1}=1404\)

=>\(3^{x-1}=27=3^3\)

=>x-1=3

=>x=4

\(x\in\left\{5,31;5,312;5,313;5,314;5,315\right\}\)

cảm ơn bn nha

a) (138,4 - 83,2) : 24 + 19,22

= 55,2 : 24 + 19,22

= 2,3 + 19,22

= 21,52

b) [6,54 + (75,4 - 29,48)] :4

= (6,54 + 45,92) :4

= 52,46 : 4

= 13,115

2..................................

a) 8,7 - x = 5,3 + 2

8,7 - x = 7,3

x = 8,7 - 7,3

x = 1,4

b) x * 5,3 = 9,01 * 4

x * 5,3 = 36,04

x = 36,04 : 5,3

x = 6,8

`x-0,7<8`

`=>x<8,7`

Mà `8<x`

`=>8<x<8,7`

Nếu `x in ZZ=>x in` $\varnothing$

`x in R=>8<x<8,7`

Ta có: x-0.7<8<x

\(\Leftrightarrow x< 8.7\)

mà 8<x

nên 8<x<8,7

Vậy: S={x|8<x<8,7}

\(X\%:3+45\%=0,7\\ \Leftrightarrow\dfrac{x}{100}:3+\dfrac{9}{20}=\dfrac{7}{10}\\ \Leftrightarrow\dfrac{x}{100}\times\dfrac{1}{3}=\dfrac{7}{10}-\dfrac{9}{20}\\ \Leftrightarrow\dfrac{x}{300}=\dfrac{14-9}{20}\\ \Leftrightarrow\dfrac{x}{300}=\dfrac{5}{20}\\ \Leftrightarrow x=\dfrac{300\times5}{20}=75\)

Vậy \(x=75\)

Câu 2 đây:

\(|x^2+|x-1||=x^2+2\)

\(\Rightarrow\orbr{\begin{cases}x^2+\left|x-1\right|=x^2+2\\x^2+\left|x-1\right|=-x^2-2\left(l\right)\end{cases}}\)

\(\Rightarrow\left|x-1\right|=2\Leftrightarrow\orbr{\begin{cases}x=3\\x=-1\end{cases}}\)

a)    \(M=\left(\frac{0,4-\frac{2}{9}+\frac{2}{11}}{1,4-\frac{7}{9}+\frac{7}{11}}-\frac{\frac{1}{3}-0,25+0,5}{1\frac{1}{6}-0,875+0,7}\right):\frac{2012}{2013}\)

\(=\left(\frac{\frac{2}{5}-\frac{2}{9}+\frac{2}{11}}{\frac{7}{5}-\frac{7}{9}+\frac{7}{11}}-\frac{\frac{1}{3}-\frac{1}{4}+\frac{1}{2}}{\frac{7}{6}-\frac{7}{8}+\frac{7}{10}}\right):\frac{2012}{2013}\)

\(=\left(\frac{2\left(\frac{1}{5}-\frac{1}{9}+\frac{1}{11}\right)}{7\left(\frac{1}{5}-\frac{1}{9}+\frac{1}{11}\right)}-\frac{2\left(\frac{1}{6}-\frac{1}{8}+\frac{1}{10}\right)}{7\left(\frac{1}{6}-\frac{1}{8}+\frac{1}{10}\right)}\right):\frac{2012}{2013}\)

\(=\left(\frac{2}{7}-\frac{2}{7}\right):\frac{2012}{2013}\)

\(=0\)

Từ 0,2 đến 4,7 có số số hạng là: \(\left(4,7-0,2\right):0,5+1=10\left(số\right)\)

⇒ Tổng 10 số đó là: \(\dfrac{\left(4,7+0,2\right)\cdot10}{2}=24,5\)

\(\left(x+0,2\right)+\left(x+0,7\right)+...+\left(x+4,7\right)=65,5\\ \Leftrightarrow10x+24,5=65,5\\ \Leftrightarrow10x=41\\ \Leftrightarrow x=4,1\)

Vậy x = 4,1

a,x=3

b,x=5,7

c,x=70/3

d,x=11

e,x=-0,5

f,x=3