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[(6x-12):2-18]x3=18
(6x-12):2-18 =18:3=6
(6x-12):2 =6+18=24
6x-12 =24x2=48
6x =48+12=60
Vậy x = 0
(6x-12):2-18=18 : 3
(6x-12):2-18= 6
(6x-12):2=6 +18
(6x-12):2=24
6x-12=24 . 2
6x-12=48
6x=48+12
6x = 60
x = 60 :6
x = 10
x+7/7=9/18x9/27
x+1=1/2x1/3
x+1=1/6
x=1/6-1
x=1/6-6/6
x=-5/6
Vậy x= -5/6
Chúc em học tốt!
Giải:
\(C=\dfrac{1}{2}.\dfrac{3}{4}.\dfrac{5}{6}...\dfrac{9999}{10000}\)
Đặt \(B=\dfrac{2}{3}.\dfrac{4}{5}.\dfrac{6}{7}...\dfrac{10000}{10001}\)
Do \(\dfrac{1}{2}< \dfrac{2}{3};\dfrac{3}{4}< \dfrac{4}{5};...;\dfrac{9999}{10000}< \dfrac{10000}{10001}\)
Nên \(C< B\) Mà \(\left\{{}\begin{matrix}C>0\\B>0\end{matrix}\right.\)
\(\Rightarrow C^2< C.B=\left(\dfrac{1}{2}.\dfrac{3}{4}...\dfrac{9999}{10000}\right)\)\(\left(\dfrac{2}{3}.\dfrac{4}{5}...\dfrac{10000}{10001}\right)\)
\(=\dfrac{1}{2}.\dfrac{2}{3}.\dfrac{3}{4}.\dfrac{4}{5}.\dfrac{5}{6}.\dfrac{6}{7}...\dfrac{9999}{10000}.\dfrac{10000}{10001}\)
\(=\dfrac{1.2.3.4.5.6...9999.10000}{2.3.4.5.6.7....10000.10001}\)
\(=\dfrac{1}{10001}< \dfrac{1}{10000}=\dfrac{1}{100}.\dfrac{1}{100}=\left(\dfrac{1}{100}\right)^2\)
\(\Rightarrow C^2< \left(\dfrac{1}{100}\right)^2\Leftrightarrow C< \dfrac{1}{100}\)
Vậy \(C=\dfrac{1}{2}.\dfrac{3}{4}.\dfrac{5}{6}...\dfrac{9999}{10000}< \dfrac{1}{100}\) (Đpcm)
a. Vì
1/2 < 2/3
3/4 < 4/5
..........
99/100<100/101 nên M<N
b.M.N=\(\frac{1.2.3.4.........100}{2.3.4.5.........101}=\frac{1}{101}\)
[ 25 + ( 6x - 18 ) : 3 ] . 2 = 78
[ 25 + ( 6x - 18 ) : 3 ] = 78 : 2
[ 25 + ( 6x - 18 ) : 3 ] = 39
( 6x - 18 ) : 3 = 39 - 25
( 6x - 18 ) : 3 = 14
6x - 18 = 14 . 3
6x - 18 = 42
6x = 42 + 18
6x = 60
x = 60 : 6
Vậy:x = 10
Hok tốt !!!
<=> 23 + 20 + 6x = 162 -18
<=> 53 + 6x = 144
<=> 6x = 91
<=> x = 91/6