Tìm x biết
\(\dfrac{7}{3}:0.2x=\dfrac{7}{6}:0.8\)
\(\dfrac{7}{3}:0.2x=\dfrac{7}{6}:0.8\)
7/3:0,2X=7/6:0,8
35/3X=35/24
X=35/24:35/3
X=1/8
7/3 : 0,2x = 7/6 : 0,8
7/3 : 0,2x = 35/24
0,2x = 7/3 : 35/24
0,2x = 8/5
x = 8/5 : 0,2
x = 8
\(\dfrac{7}{3}:0.2x=\dfrac{7}{6}:0.8\)
7/3:0.2x=7/6:0.8
7/3 : 0.2 x = 35/24
0.2 x = 35/24 : 7/3
0.2 x = 5/8
x=5/8 : 0.2
x= 25/8
Vậy x=25/8
=>\(\dfrac{7}{3}:0,2x=\dfrac{7}{6}.\dfrac{5}{4}\)
=>\(\dfrac{7}{3}:0,2x=\dfrac{35}{24}\)
=>0,2\(.x=\dfrac{7}{3}:\dfrac{35}{24}\)
=>0,2\(.x=\dfrac{7}{3}.\dfrac{24}{35}\)
=>0,2.\(x=\dfrac{8}{5}\)
=>\(x=\dfrac{8}{5}:0,2\)
=>\(x=\dfrac{8}{5}.5\)
=>\(x=8\)
Vậy x=8
Tìm x, biết :
a) \(\dfrac{\text{x}}{3}\) = \(\dfrac{2}{3}\) + \(\dfrac{-1}{7}\)
b) \(\dfrac{-5}{6}-x\) = \(\dfrac{7}{12}+\dfrac{-1}{3}\)
Tìm x,y biết :
6) 3x=4y và 2x + 3y = 7
7) \(\dfrac{x}{5}=\dfrac{y}{6}=\dfrac{z}{7}\) và x-y+z=36
8) \(\dfrac{x}{2}=\dfrac{y}{3}=\dfrac{z}{6}\) và 3x-2y+2z = 24
7) vì \(\dfrac{x}{5}\)=\(\dfrac{y}{6}\)=\(\dfrac{z}{7}\)và x-y+z=36
Nên theo tính chất của dãy tỉ số bằng nhau ta có:
\(\dfrac{x}{5}\)=\(\dfrac{y}{6}\)=\(\dfrac{z}{7}\)=\(\dfrac{x-y+z}{5-6+7}\)=\(\dfrac{36}{6}\)=6
\(\Rightarrow\)x=6.5=30
y=6.6=36
z=6.7=42
vậy x=30,y=36,z=42
Tìm x biết: a) x + \(\dfrac{2}{3}=\dfrac{4}{27}\) b) \(\dfrac{3}{4}x-\dfrac{7}{3}=\dfrac{1}{4}x+\dfrac{1}{6}\)
c) \(\dfrac{13}{10}x-\dfrac{5}{2}=\dfrac{7}{2}\) d) (3\(x\) + 2) \(\left(\dfrac{-2}{5}x-7\right)=0\)
a: x=4/27-2/3=4/27-18/27=-14/27
b: =>3/4x-1/4x=1/6+7/3
=>1/2x=1/6+14/6=5/2
hay x=5
c: =>13/10x=7/2+5/2=6
=>x=13/10:6=13/60
d: (3x+2)(-2/5x-7)=0
=>3x+2=0 hoặc 2/5x+7=0
=>x=-2/3 hoặc x=-35/2
a: x=4/27-2/3=4/27-18/27=-14/27
b: =>3/4x-1/4x=1/6+7/3
=>1/2x=1/6+14/6=5/2
hay x=5
c: =>13/10x=7/2+5/2=6
=>x=13/10:6=13/60
d: (3x+2)(-2/5x-7)=0
=>3x+2=0 hoặc 2/5x+7=0
=>x=-2/3 hoặc x=-35/2
Tìm x biết: x - 1 = \(\dfrac{6}{7}\) + \(\dfrac{1}{7}\) x\(\dfrac{2}{7}\) + \(\dfrac{1}{7}\) x \(\dfrac{5}{7}\)
\(\Rightarrow x-1=\dfrac{6}{7}+\dfrac{1}{7}\times\left(\dfrac{2}{7}+\dfrac{5}{7}\right)=\dfrac{6}{7}+\dfrac{1}{7}\times1\\ \Rightarrow x-1=\dfrac{6}{7}+\dfrac{1}{7}=1\\ \Rightarrow x=1+1=2\)
Tìm x biết x - \(\dfrac{3}{5}\) = \(\dfrac{2}{7}\) + \(\dfrac{1}{6}\)
\(x-\dfrac{3}{5}=\dfrac{2}{7}+\dfrac{1}{6}\)
\(\Leftrightarrow x-\dfrac{3}{5}=\dfrac{19}{42}\)
\(\Leftrightarrow x=\dfrac{19}{42}+\dfrac{3}{5}\)
\(\Leftrightarrow x=\dfrac{221}{210}\)
=>x-3/5=12/42+7/42=19/42
=>x=19/42+3/5=95/210+126/210=221/210
x-3/5=2/7+1/6
x-3/5=12/42+7/42
x-3/5=19/42
x=19/42+3/5
x=95/210 + 126/210
x=221/210
1) Tính
\(\dfrac{7^4.3-7^3}{7^4.6-7^3.2}\) ; \(\dfrac{10^3+5.10^2+5}{6^3+3.6^2+3^2}\) ; \(E=1+\dfrac{1}{3}+\dfrac{1}{3^2}+...+\dfrac{1}{3^{100}}\)
2) Tìm x biết
\(\dfrac{1}{1.2}+\dfrac{1}{2.3}+\dfrac{1}{3.4}+...+\dfrac{1}{x.\left(x+1\right)}\) ; \(3^{x+1}+3^{x+3}=810\)
MN ƠI ! GIÚP MIK VS > . <
Bài 1:
a) Ta có: \(\dfrac{7^4\cdot3-7^3}{7^4\cdot6-7^3\cdot2}\)
\(=\dfrac{7^3\cdot\left(7\cdot3-1\right)}{7^3\cdot2\left(7\cdot3-1\right)}\)
\(=\dfrac{1}{2}\)
c) Ta có: \(E=1+\dfrac{1}{3}+\dfrac{1}{3^2}+...+\dfrac{1}{3^{100}}\)
\(\Leftrightarrow\dfrac{1}{3}\cdot E=\dfrac{1}{3}+\dfrac{1}{3^2}+\dfrac{1}{3^3}+...+\dfrac{1}{3^{101}}\)
\(\Leftrightarrow E-\dfrac{1}{3}\cdot E=1+\dfrac{1}{3}+\dfrac{1}{3^2}+...+\dfrac{1}{3^{100}}-\left(\dfrac{1}{3}+\dfrac{1}{3^2}+\dfrac{1}{3^3}+...+\dfrac{1}{3^{101}}\right)\)
\(\Leftrightarrow E\cdot\dfrac{2}{3}=1-\dfrac{1}{3^{101}}\)
\(\Leftrightarrow E=\dfrac{3-\dfrac{3}{3^{101}}}{2}=\dfrac{1-\dfrac{1}{3^{100}}}{2}\)
Tìm x biết:
a, \(\dfrac{x^2}{6}\)= \(\dfrac{36}{x}\)
b, \(\dfrac{x}{3}\)=\(\dfrac{y}{7}\)=\(\dfrac{z}{2}\)
\(a)\dfrac{x^2}{6}=\dfrac{36}{x}\)
\(=>x^3=36.6\)
\(=>x^3=6^3\)
\(=>x=6\)
(câu b thiếu dữ kiện)
áp dụng dãy tỉ số bằng nhau ta có
x/3=y/7=z/2=x+y+z/3+7+2=-16/12=-4/3
=>x/3=-4/3=>x=-4/3X3=-4
=>y/7=-4/3=>y=-4/3X7=-9,(3)
=>z/2=-4/3=>z=-4/3X2=-2(6)
b, \(\dfrac{x}{3}\)= \(\dfrac{y}{7}\)= \(\dfrac{z}{2}\) Mà x+ y+ z= -16
_xl mk bị thiếu mất vế sau ^^_