Lời giải:
$12=2^2.3$

$5=1.5$

$8=2^3$

$\Rightarrow \text{BCNN(12,5,8)}=2^3.3.5=120$

$x\in \text{BC(12,5,8)}$ nên $x\in \left\{120; 240; 360;...\right\}$

Mà $60\leq x\leq 240$ nên $x\in \left\{120; 240\right\}$

\(\frac{2x-9}{240}=\frac{39}{80}\)

<=> \(\left(2x-9\right)\cdot80=240\cdot39\)

<=> \(160x-720=9360\)

<=> \(160x=10080\)

<=> \(x=63\)

\(\left|x-8\right|+12=25\)

<=> \(\left|x-8\right|=13\)

<=> x - 8 = 13 hoặc x - 8 = -13

<=> x = 21 hoặc x = -5

(2x-9):3/240:3 =39/80

2x:3-3/80=39/80

=>2x:3 =39

    2x    = 39:3

    2x =13 

    x = 13 :2 

    x = 13/2

b)x - 8 =25 -12

   x - 8 = 13

   x      =  13 +8  

   x      = 21

ok rồi đó :))

ai trả lời đầu tiên mình tick choa :)

C

C nha Gia Long

\(\frac{240}{x-12}-\frac{240}{x}=\frac{5}{3}\)

\(\Leftrightarrow\frac{240}{x-12}-\frac{240}{x}=\frac{5}{3}\left(x\ne12,x\ne0\right)\)

\(\Leftrightarrow\frac{240}{x-12}-\frac{240}{x}-\frac{5}{3}=0\)

\(\Leftrightarrow\frac{720x-720x+8640-5x^2+60x}{3x\left(x-12\right)}=0\)

\(\Leftrightarrow8640-5x^2+60x=0\)

\(\Leftrightarrow5\left(1728-x^2+12x\right)=0\)

\(\Leftrightarrow5\left(-x^2+12x+1728\right)=0\)

\(\Leftrightarrow5\left(-x^2+48x-36x+1728\right)=0\)

\(\Leftrightarrow5\left[-x\left(x-48\right)-36\left(x-48\right)\right]=0\)

\(\Leftrightarrow5\left[-\left(x-48\right)\right].\left(x+36\right)=0\)

\(\Leftrightarrow-5\left(x-48\right).\left(x+36\right)=0\)

\(\Leftrightarrow\left(x-48\right)\left(x+36\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x-48=0\\x+36=0\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=48\\x=-36\end{matrix}\right.,x\ne12,x\ne0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=48\\x=-36\end{matrix}\right.\)

8000 : 2 = ?

Nhẩm: 8 nghìn : 4 = 2 nghìn

Vậy 8000 : 4 = 2000

40000 : 5 = ?

Nhẩm: 40 nghìn : 5 = 8 nghìn

Vậy 40 000 : 5 = 8000

36000: 9 = ?

Nhẩm: 36 nghìn : 9 = 4 nghìn

Vậy 36 000 : 9 = 4000

42000 : 7 = ?

Nhẩm: 42 nghìn : 7 = 6 nghìn

Vậy 42 000 : 7 = 6000

\(a.\frac{6}{240}=\frac{1}{40};\frac{12}{240}=\frac{1}{20};\frac{15}{240}=\frac{1}{16};\frac{60}{240}=\frac{1}{4}\)

\(b.\frac{6}{336}=\frac{1}{56};\frac{8}{336}=\frac{1}{42};\frac{52}{336}=\frac{13}{84};\frac{56}{336}=\frac{1}{6}\)

a) 6/240=1/40 ; 12/240=1/20 ; 15/240=1/16 ; 60/240=1/4

b) 6/336=1/56 ; 8/336=1/42 ; 52/336=13/84 ; 56/336=1/6

a) \(\frac{1}{40}\);\(\frac{1}{20}\);\(\frac{1}{16}\);\(\frac{1}{4}\)

b) \(\frac{1}{56}\);\(\frac{1}{42}\);\(\frac{13}{84}\);\(\frac{1}{6}\)

mk nhanh nhất