1/3*5 +1/3*5 + 1/5*7 + ... 1/x*(x+2)=20/21
1. Tìm x:
1, 7/20 - |2/5 + x| = 10/21
2, |3/7 - x| - (-2/3) = 1+1/2
3, -1/2 + |1/3x + 2/5| = 5/7 x 3/11 + 8/11 x 5/7
2. Tìm GTNN của biểu thứ
B= |x-3| - |x+5|
Bài 1:
1: 7/20-|x+2/5|=10/21
=>|x+2/5|=-53/420(vô lý)
2: \(\left|\dfrac{3}{7}-x\right|-\left(-\dfrac{2}{3}\right)=1+\dfrac{1}{2}\)
\(\Leftrightarrow\left|x-\dfrac{3}{7}\right|=\dfrac{3}{2}-\dfrac{2}{3}=\dfrac{5}{6}\)
=>x-3/7=5/6 hoặc x-3/7=-5/6
=>x=53/42 hoặc x=-17/42
1. Tìm x:
1, 7/20 - |2/5 + x| = 10/21
2, |3/7 - x| - (-2/3) = 1+1/2
3, -1/2 + |1/3x + 2/5| = 5/7 x 3/11 + 8/11 x 5/7
2. Tìm GTNN của biểu thứ
B= |x-3| - |x+5|
3: \(-\dfrac{1}{2}+\left|\dfrac{1}{3}x+\dfrac{2}{5}\right|=\dfrac{5}{7}\cdot\dfrac{3}{11}+\dfrac{8}{11}\cdot\dfrac{5}{7}=\dfrac{5}{7}\)
=>|1/3x+2/5|=5/7+1/2=17/14
=>1/3x+2/5=17/14 hoặc 1/3x+2/5=-17/14
=>x=171/70 hoặc x=-339/70
Thực hiện phép tính:
A) 7/38 x 9/11 +7/38 x 4/11 -7/38 x 2/11
B) 5/31 x 21/25 + 5/31 x -7/10 - 5/31 x 9/20
C) ( -2/3 + 3/7 ) : 4/5 + (-1/3 + 4/7 ) : 4/5
D) 5/9 : ( 1/11 -5/22 ) + 5/9 : ( 1/15 - 2/3 )
E) 3/14 : 1/28 -13/21 : 1/28 + 29/42 : 1/28 - 8
F) ( -40/51 x 0,32 x17/20) : 64/75
Đây là dấu x ( là nhân ) mọi người nhé
mong mn giúp em ạ
A) 7/38 x 9/11 +7/38 x 4/11 -7/38 x 2/11
=7/38.(9/11+4/11-2/11)
=7/38
B) 5/31 x 21/25 + 5/31 x -7/10 - 5/31 x 9/20
=5/31.(21/25-7/10-9/20)
=5/31.(-31/100)
=-1/20
a) (-1,25).17/21.(-0,4).7/34
b)0,5\(^{^{x+1}}\) + 0,5\(^x\) = 1,5
c) x:20-25%x=-1\(\dfrac{1}{5}\)
d) (x-1)\(^2\) =1
e) 5\(^3\) : 25+2\(^4\) :4
a: \(=\dfrac{5}{4}\cdot\dfrac{2}{5}\cdot\dfrac{17}{21}\cdot\dfrac{7}{34}=\dfrac{1}{2}\cdot\dfrac{1}{2}\cdot\dfrac{1}{3}=\dfrac{1}{12}\)
b: =>0,5^x(0,5+1)=1,5
=>0,5^x=1
=>x=0
c: =>x*0,05-0,25*x=-1,2
=>-0,3*x=-1,2
=>x=4
d: =>x-1=1 hoặc x-1=-1
=>x=0 hoặc x=2
e: =5+4=9
thực hiện phép tính :
a, -1/2 + 19/23+ -9/2+ 4/23 +3 /-6
b. 5/13+ -5/7 +-20/41 + 8/13 +-21/41
c.-5/7 x 19/41 + 5/7 x -21/41 + 5/7
d. 7/3 +1/2 - -3/70
Đây là phân số
Chọn câu trả lời đúng \(\left(2x+\dfrac{1}{5}\right)\left(-\dfrac{3}{5}x+\dfrac{4}{7}\right)=0\) thì:
A. x = \(\dfrac{-1}{10}\) hoặc x = \(\dfrac{20}{21}\)
B. x = \(\dfrac{20}{21}\)
C. x = \(-\dfrac{1}{10}\)
D. x = \(-\dfrac{20}{21}\)
a,1/3 .(x-2/5)=3/4 b, 7/3:(x-2/3)=4/5 c,1/3.(x-2/5)=4/5 d, 2/3.(x-1/2)-1/4.(x-2/5)=7/3 e,3/7 .(x-2/3)+1/2=5/4.(x-2) f,1/2.(x-3)+1/3.(x-4)+1/4.(x-5)=1/5 g,[2/3.(x-1/2)-4/5]:(x-1/3)=21/5 h, {x-[1/2.(x-3)+11/5]}:(x-1/2)=3/5 i,x.(x-2/5)-(x+2).x+11/4=4/3
a: =>x-2/5=3/4:1/3=3/4*3=9/4
=>x=9/4+2/5=45/20+8/20=53/20
b: =>x-2/3=7/3:4/5=7/3*5/4=35/12
=>x=35/12+2/3=43/12
c: 1/3(x-2/5)=4/5
=>x-2/5=4/5*3=12/5
=>x=12/5+2/5=14/5
d: =>2/3x-1/3-1/4x+1/10=7/3
=>5/12x-7/30=7/3
=>5/12x=7/3+7/30=77/30
=>x=77/30:5/12=154/25
e: \(\Leftrightarrow x\cdot\dfrac{3}{7}-\dfrac{2}{7}+\dfrac{1}{2}-\dfrac{5}{4}x+\dfrac{5}{2}=0\)
=>\(x\cdot\dfrac{-23}{28}=\dfrac{2}{7}-3=\dfrac{-19}{7}\)
=>x=19/7:23/28=76/23
f: =>1/2x-3/2+1/3x-4/3+1/4x-5/4=1/5
=>13/12x=1/5+3/2+4/3+5/4=257/60
=>x=257/65
i: =>x^2-2/5x-x^2-2x+11/4=4/3
=>-12/5x=4/3-11/4=-17/12
=>x=17/12:12/5=85/144
Bạn nào giúp mik giải bài toán này với:
* ( 3/10 - 4/15 - 7/20 ) x 5/19 tất cả trên ( 1/14 + 1/7 - âm 3/35 ) x âm 4/3
*( 1+2+3+...+100) x (1/3 -1/5 -1/7 -1/9) x (6,3 x 12 - 21 x 3,6) tất cả trên 1/2 + 1/3 + 1/4 +....+1/100
*\(\frac{\left(\frac{3}{10}-\frac{4}{15}-\frac{7}{20}\right).\frac{5}{19}}{\left[\frac{1}{14}+\frac{1}{7}-\left(-\frac{3}{35}\right)\right].\frac{4}{3}}=\frac{\left(\frac{18}{60}-\frac{16}{60}-\frac{21}{60}\right).\frac{5}{19}}{\left(\frac{5}{70}+\frac{10}{70}+\frac{6}{70}\right).\frac{4}{3}}=\frac{\frac{-19}{60}.\frac{5}{19}}{\frac{21}{70}.\frac{4}{3}}=\frac{\frac{-1}{12}}{\frac{14}{35}}=-\frac{1}{12}.\frac{35}{14}=\frac{-35}{168}\)
*\(\frac{\left(1+2+3+...+100\right).\left(\frac{1}{3}-\frac{1}{5}-\frac{1}{7}-\frac{1}{9}\right).\left(6,3.12-21.3,6\right)}{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{100}}\)
=\(\frac{\left(1+2+3+...+100\right)\left(\frac{1}{3}-\frac{1}{5}-\frac{1}{7}-\frac{1}{9}\right).\left(\frac{63}{10}.12-21.\frac{18}{5}\right)}{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{100}}\)
=\(\frac{\left(1+2+3+...+100\right)\left(\frac{1}{3}-\frac{1}{5}-\frac{1}{7}-\frac{1}{9}\right).\left(\frac{378}{5}-\frac{378}{5}\right)}{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{100}}\)
=\(\frac{\left(1+2+3+...+100\right)\left(\frac{1}{3}-\frac{1}{5}-\frac{1}{7}-\frac{1}{9}\right).0}{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{100}}=0\)
5. \(3-1\dfrac{1}{2}-x+\dfrac{5}{4}=2-\left|1\dfrac{1}{8}-\dfrac{5}{12}\right|\) 6. \(3\dfrac{1}{14}-5\dfrac{1}{3}-\dfrac{4}{7}+\dfrac{11}{21}=x-\dfrac{1}{2}\) 7. \(\dfrac{11}{-40}+\dfrac{4}{5}-\left|\dfrac{3}{4}-1\dfrac{5}{12}\right|=\dfrac{3}{20}-x\)
chắc h có mấy thành cay r nên ko làm bn lên mạng tải phẩn mêm có cánh iair đó :D
\(3-1\dfrac{1}{2}-x+\dfrac{5}{4}=2-\left|1\dfrac{1}{8}-\dfrac{5}{12}\right|\)
\(3-1\dfrac{1}{2}-x+\dfrac{5}{4}=2-\dfrac{17}{24}\)
\(x=3-1\dfrac{1}{2}+\dfrac{5}{4}-2+\dfrac{17}{24}\)
\(x=\dfrac{35}{24}\)
bn làm từng bước nhé :D