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Ta có: 1/1x2 + 1/2x3 + 1/3x4 +...+ 1/X x (X + 1) = 499/500
=> 1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 +...+ 1/X - 1/(X + 1) = 499/500
=> 1 - 1/(X + 1) = 499/500
=> 1/(X + 1) = 1 - 499/500
=> 1/(X + 1) = 1/500
=> X + 1 = 500
=> X = 500 - 1
=> X = 499
Đáp số: X = 499
x - 58 : 2 = 17
x - 29 = 17
x = 17 + 29
x = 46
( x - 58 ) : 2 = 17
x - 58 = 17 x 2
x - 58 = 34
x = 34 + 58
x = 92
125 + ( 145 - x ) = 175
145 - x = 175 - 125
145 - x = 50
x = 145 - 50
x = 95
\(x\times\frac{2}{5}=\frac{4}{5}:\frac{2}{3}\)
\(x\times\frac{2}{5}=\frac{6}{5}\)
\(x=\frac{6}{5}:\frac{2}{5}\)
\(x=3\)
x + 3,75 + 4x = 24,25
x + 4x = 24,25 - 3,75
x * 5 = 20,5
x = 20,5 : 5
x= 4,1
x - 58 : 2 = 17
x - 29 = 17
x = 17 + 29
x = 46
( x - 58 ) : 2 = 17
x - 58 = 17 x 2
x - 58 = 34
x = 34 + 58
x = 92
125 + ( 145 - x ) = 175
145 - x = 175 - 125
145 - x = 50
x = 145 - 50
x = 95
x.2/5=4/5:2/3
x.2/5=6/5
x=6/5:2/5
=3
x + 3,75 + 4x = 24,25
x + 4x = 24,25 - 3,75
x * 5 = 20,5
x = 20,5 : 5
x= 4,1
Theo đề bài, ta có: \(\left(xyz\right)^2=\frac{1}{3}\cdot\left(-\frac{2}{5}\right)\cdot\left(-\frac{3}{10}\right)=\frac{1}{25}\)
\(\rightarrow xyz=\sqrt{\frac{1}{25}}=+_-\frac{1}{5}\)
Th1: xyz = 1/5
=> z= xyz : xy = 1/5 : 1/3 = 3/5
=> x= xyz : yz = 1/5 : (-2/5) = -1/2
=> y = xyz : xz = 1/5 : (-3/10) = -2/3
Th2: xyz = -1/5
=> z= xyz : xy = -1/5 : 1/3 = -3/5
=> x= xyz : yz = -1/5 : (-2/5) = 1/2
=> y = xyz : xz = -1/5 : (-3/10) = 2/3
Vậy....
Ta có: 4/5:4/7=4/5x7/4=7/5=>7/5>1>0
2/5x10/3=4/3=>4/3>1>0
7/5=42/30
4/3=40/30
Vì: 42/30>41/30>40/30
=>X=41/30
\(x+\frac{1}{2}+x+\frac{1}{4}+x+\frac{1}{8}+x+\frac{1}{16}=\frac{23}{16}=>4x=\frac{23}{16}-\frac{15}{16}=\frac{1}{2}=>x=\frac{1}{8}\)
(xx4)+1/2+1/4+1/8+1/16=23/16
xx4=23/16-(1/2+1/4+1/8+1/16)
xx4=1/2
x=1/2:4
x=1/8
Đúng 100% nhé Nhớ k cho mình đấy
\(\frac{1}{10}\cdot\frac{2}{3}\cdot\frac{3}{4}\cdot\frac{4}{5}\cdot\frac{5}{6}\cdot\frac{6}{5}\cdot\frac{5}{4}\cdot\frac{4}{3}\cdot\frac{3}{2}=\frac{1}{10}\)
\(\frac{1}{10}\times\frac{2}{3}\times\frac{3}{4}\times\frac{4}{5}\times\frac{5}{6}\times\frac{6}{5}\times\frac{5}{4}\times\frac{4}{3}\times\frac{3}{2}\)\(\frac{3}{2}\)
\(=\frac{1}{10}\times\left(\frac{2}{3}\times\frac{3}{2}\right)\times\left(\frac{3}{4}\times\frac{4}{3}\right)\times\left(\frac{4}{5}\times\frac{5}{4}\right)\times\left(\frac{5}{6}\times\frac{6}{5}\right)\)
\(=\frac{1}{10}\times1\times1\times1\times1\)
\(=\frac{1}{10}\)
#Chúc bạn học tốt !
#k cho mình nhé ?
1/3x-2/5(x+1)=0
1/3x-2/5x-2/5=0
-1/15x-2/5=0
-1/15x=6/15
x=-6
\(A=\frac{1}{3}.x-\frac{2}{5}.\left(x+1\right)=\)\(0\)
\(A=\frac{1}{3}.x-\frac{2}{5}x-\frac{2}{5}\)\(=0\)
\(A=x.\left(\frac{1}{3}-\frac{2}{5}\right)-\frac{2}{5}\)\(=0\)
\(A=x.\frac{-1}{15}=\frac{2}{5}\)
\(A=\frac{2}{5}\div\frac{-1}{15}\)
\(A=-6\)
Vậy \(A=-6\)