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Câu b:
\(\frac{21}{8}:\frac{5}{6}+\frac{1}{2}:\frac{5}{6}\)
= \(\frac{63}{20}+\frac{3}{5}\)
= \(\frac{15}{4}\)
\(\left(\frac{21}{8}+\frac{1}{2}\right):\frac{5}{6}\)
\(\frac{25}{8}:\frac{5}{6}\)
\(\frac{25}{8}.\frac{6}{5}\)
\(\frac{30}{8}\)
720:[41-(2×x-5)]=120
[41-(2×x-5)]=720:120
[41-(2×x-5)]=6
(2×x-5)=41-6
(2×x-5)=35
2×x=35+5
2x=40
x=40:2
vậy x=20
a) \(720:\left[41-\left(2x-5\right)\right]=120\)
\(\Rightarrow\left[41-\left(2.x-5\right)\right]=6\)
\(\Rightarrow2x-5=35\Rightarrow2x=40\Rightarrow x=20\)
b) \(4,8.5-x+100=250\)
\(\Rightarrow4,8.5-x=150\Rightarrow24-x=150\Rightarrow x=-126\)
c)+) \(\frac{3}{5}+\frac{2}{5}:x=1\Rightarrow\frac{2}{5}:x=\frac{2}{5}\Rightarrow x=1\)
+) \(\frac{3}{5}+\frac{2}{5}:x=\frac{1}{4}\Rightarrow\frac{2}{5}:x=\frac{-7}{20}\Rightarrow x=\frac{-8}{7}\)
Cậu có thể tham khảo bài làm trên đây ạ, chúc cậu hok tốt ^^
Chỉ làm bài khó thôi nhé:::::::::::::::
\(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+...+\frac{2}{x.\left(x+1\right)}=\frac{2016}{2018}\)
\(\Rightarrow\frac{2}{6}+\frac{2}{12}+\frac{2}{20}+....+\frac{2}{x.\left(x+1\right)}=\frac{2016}{2018}\)
\(\Rightarrow2.\left(\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{x.\left(x+1\right)}\right)=\frac{2016}{2018}\)
\(\Rightarrow\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{x.\left(x+1\right)}=\frac{1013}{2018}\)
\(\Rightarrow\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{x}-\frac{1}{x+1}=\frac{1013}{2018}\)
\(\Rightarrow\frac{1}{2}-\frac{1}{x+1}=\frac{1013}{2018}\)
\(\Rightarrow\frac{1}{x+1}=\frac{1}{2018}\Rightarrow x+1=2018\Rightarrow x=2017\)
\(a,30+X=120:5+27\\ 30+X=24+27\\ 30+X=51\\ X=51-30=21\\ ---\\ b,40-3\times X=13\\ 3\times X=40-13=27\\ X=\dfrac{27}{3}=9\\ ---\\ 2\times X-8=16\\ 2\times X=16+8\\ 2\times X=24\\ X=\dfrac{24}{2}=12\\ \\---\\ \dfrac{1}{2}\times X-\dfrac{1}{3}=\dfrac{1}{4}\\ \dfrac{1}{2}\times X=\dfrac{1}{4}+\dfrac{1}{3}=\dfrac{7}{12}\\ X=\dfrac{7}{12}:\dfrac{1}{2}=\dfrac{7}{6}\)
a)13/17 < 15/19
a) 2/3 x X + 3/4 = 3
2/3 x X = 3 - 3/4
2/3 x X = 9/4
X = 9/4 : 2/3
X = 27/8
a. Ta có : \(\frac{13}{17}=\frac{247}{323};\frac{15}{19}=\frac{255}{323}\)
Vì 255 > 247 nên 247/323 < 255/323
Hay \(\frac{13}{17}< \frac{15}{19}\)
b. \(\frac{2}{3}\times x+\frac{3}{4}=3\)
\(\frac{2}{3}\times x=3-\frac{3}{4}\)
\(\frac{2}{3}\times x=\frac{9}{4}\)
\(x=\frac{9}{4}:\frac{2}{3}\)
\(x=\frac{27}{8}\)
c. \(720:\left[41-\left(2\times x-5\right)\right]=120\)
\(\left[41-\left(2\times x-5\right)\right]=720:120\)
\(41-\left(2\times x-5\right)=6\)
\(2\times x-5=35\)
\(2\times x=40\)
\(x=20\)
mình biết kết quả là 20 nhưng chưa biết cách làm. Bạn nào biết thì giúp mình với. Mình k cho!!!
a, (17x-25):8=81-65
(17x-25):8=16
17x-25=16:8
17x-25=2
17x=2+25
17x=27
x=27:17
x=27/17
b,720:[41-(2x-5)]=40
41-(2x-5)=720:40
41-(2x-5)=18
2x-5=41-18
2x-5=23
2x=23+5
2x=28
x=28:2
x=14
c,231-(x-6)=103
x-6=231-103
x-6=128
x=128+6
x=134
XEM LẠI GIÙM MÌNH BẠN NHA!
đề bài: (17x-25):8+65= 81
(17x-25):8=81-65=16
17x-25= 16 . 8= 128
17x = 128+25=153
x = 153:17=9
b, Đề bài 720:[41-(2x-5)]=8.5
720:[41-(2x-5)]=40
41-(2x-5)=720:40=18
2x-5=41-18=23
2x = 23+5=28
x = 28:2= 14
c, 231-(x-6)=1339:13=103
x-6=231-103=128
x= 128 + 6= 134
Đúng thì **** bạn
720 : [ 41 - ( 2 x x -5 ) =120
41 - ( 2 x x - 5 ) = 720 : 120
41 - ( 2 x \(x\) -5 ) =6
2 x \(x\) -5 = 41 - 6
2 x \(x\) - 5 = 35
2 x \(x\) = 35+5
2 x \(x\)=40
\(x\) = 40 : 2 = 20
Vậy x = 20
Ủng hộ nhé ^^
720 : [ 41 - ( 2 x X - 5 ) ] = 120
41 - ( 2 x X - 5 ) = 720 : 120
41 - ( 2 x X - 5 ) = 6
2 x X - 5 = 41 - 6
2 x X - 5 = 35
2 x X = 35 - 5
2 x X = 30
X = 30 : 2
X = 15
Học tốt nhé bạn !
Bai 1 :
27 x 36 + 27 x 45 - 27
= 27 x 36 + 27 x 45 - 27 x 1
= 27 x ( 36 + 45 - 1 )
= 27 x 80
= 21260
Bai 2 :
a) 720 : [ 41 - ( 2 . x - 5 ) ] = 120
41 - ( 2 . x - 5 ) = 720 : 120
41 - ( 2 . x - 5 ) = 6
2 . x - 5 = 41 - 6
2 . x - 5 = 35
2 . x = 35 + 5
2 . x = 40
x = 40 : 2
x = 20
b) ( 3,7 : x - 13 ) x 0,2 - 1,4 = 10,8
( 3,7 : x - 13 ) x 0,2 = 10,8 + 1,4
( 3,7 : x - 13 ) x 0,2 = 12,2
3,7 : x - 13 = 12,2 : 0,2
3,7 : x - 13 = 61
3,7 : x = 61 + 13
3,7 : x = 74
x = 74 : 3,7
x = 20
a.27x36+27x45-27
=27x(36+45-1)
=27x80
=2160
a. 720:[41-(2*x-5)]=120
41-(2*x-5)=720:120=6
2*x-5=41-6=35
2*x=35+5=40
x=40:2=20
Vậy x=20
b. (3,7:x-13)x0,2-1,4=10,8
(3,7:x-13)x0,2=10,8+1,4=11,2
3,7:x-13=11,2:0,2=56
3,7:x=56+13=69
x=3,7:69=\(\frac{37}{690}\)