tìm x biết
x/3 -3/7+2/5=31/140
tìm x biết
x/7-3/7+1/2=31/140
5/12+5/x-1/8=1/2
Bài làm
a) \(\frac{x}{7}-\frac{3}{7}+\frac{1}{2}=\frac{31}{140}\)
\(\frac{x}{7}=\frac{31}{140}-\frac{1}{2}+\frac{3}{7}\)
\(\frac{x}{7}=\frac{31}{140}-\frac{70}{140}+\frac{60}{140}\)
\(\frac{x}{7}=\frac{21}{140}\)
\(\frac{x}{7}=\frac{3}{20}\)
=> \(x.20=3.7\)
=> \(x=\frac{3.7}{20}\)
=> \(x=\frac{21}{20}\)
Vậy \(x=\frac{21}{20}\)
b) \(\frac{5}{12}+\frac{5}{x}-\frac{1}{8}=\frac{1}{2}\)
\(\frac{5}{x}=\frac{1}{2}+\frac{1}{8}-\frac{5}{12}\)
\(\frac{5}{x}=\frac{12}{24}+\frac{3}{24}-\frac{10}{24}\)
\(\frac{5}{x}=\frac{5}{24}\)
=> \(5.24=5.x\)
=> \(x=\frac{5.24}{5}\)
=> \(x=24\)
Vậy \(x=24\)
# Học tốt #
Tìm x, biết
x=7/25 + -1/5
x=5/11 + 4/-9
5/9 - x/-1=-1/3
\(x=\dfrac{7}{25}+\dfrac{-1}{5}=\dfrac{7}{25}-\dfrac{1}{5}=\dfrac{2}{25}.\\ x=\dfrac{5}{11}+\dfrac{4}{-9}=\dfrac{5}{11}-\dfrac{4}{9}=\dfrac{1}{99}.\\ \dfrac{5}{9}-\dfrac{x}{-1}=\dfrac{-1}{3}\Leftrightarrow\dfrac{5}{9}+x=-\dfrac{1}{3}.\Leftrightarrow x=-\dfrac{8}{9}.\)
\(x=\dfrac{7}{25}+-\dfrac{1}{5}=>\dfrac{7}{25}+-\dfrac{5}{25}=>x=\dfrac{2}{25}\)
\(x=\dfrac{5}{11}+\dfrac{4}{-9}=>\dfrac{-45}{-99}+\dfrac{44}{-99}=>x=\dfrac{-1}{-99}=\dfrac{1}{99}\)
\(\dfrac{5}{9}-\dfrac{x}{-1}=-\dfrac{1}{3}=>-\dfrac{1}{3}-\dfrac{5}{9}=>\dfrac{x}{-1}=-\dfrac{8}{9}=>x=-\dfrac{8}{9}\)
\(x=\dfrac{7}{25}+\dfrac{-1}{5}\\ \Rightarrow x=\dfrac{7}{25}+\dfrac{-5}{25}\\ \Rightarrow x=\dfrac{2}{25}\\ x=\dfrac{5}{11}+\dfrac{4}{-9}\\ \Rightarrow x=\dfrac{-45}{-99}+\dfrac{44}{-99}\\ \Rightarrow x=\dfrac{45}{99}+\dfrac{44}{99}\\ \Rightarrow x=\dfrac{95}{99}\\ \dfrac{5}{9}-\dfrac{x}{-1}=\dfrac{-1}{3}\\ \Rightarrow\dfrac{x}{-1}=\dfrac{5}{9}-\dfrac{-1}{3}\\ \Rightarrow\dfrac{x}{-1}=\dfrac{5}{9}-\dfrac{-3}{9}\\ \Rightarrow\dfrac{x}{-1}=\dfrac{8}{9}\Rightarrow x\cdot9=-1\cdot8=-8\\ \Rightarrow x\cdot9=-8\\ \Rightarrow x=\dfrac{-8}{9}\)
Tìm x
a, x+1/9-3/5=3/6
b, 3/4-x+6/-11=5/6
C, X/4-3/7+2/5=31/140
D, 5/12+5/X-1/8=1/2
a, x + 1/9 - 3/5 = 3/6
x + 1/9 = 3/6 - 3/5
x + 1/9 = -1/10
x = -1/10 - 1/9
x = -19/90
720 : ( x . 2 + x . 3 ) = 3.2
720 : ( x . 2 + x.3 ) = 6
( x .2 + x.3 ) = 720 : 6
x.2+x.3 = 120
x . ( 2 + 3 ) = 120
x . 5 = 120
x = 120 : 5
x = 24
Bài 1 Tìm x biết
x= 3/4 cộng 1/-12
x/14 = 1/7 cộng -3/14
Bài 2 Tính một cách hợp lí
A= 2/7 cộng -3/8 cộng 11/7 cộng 1/3 cộng 1/7 cộng 5/-8
B= 3/17 cộng -5/13 cộng -18/35 cộng 14/17 cộng 17/-35 cộng -8/13
\(\frac{x}{4}-\frac{3}{7}+\frac{2}{5}=\frac{31}{140}\)
\(\frac{x}{4}-\frac{3}{7}+\frac{2}{5}=\frac{31}{140}\)
\(\frac{x}{4}=\frac{31}{140}-\frac{2}{5}+\frac{3}{7}\)
\(\frac{x}{4}=\frac{1}{4}\)
\(\Rightarrow x=1\)
\(\frac{x}{4}-\frac{3}{7}+\frac{2}{5}=\frac{31}{140}\)
\(\frac{x}{4}-\frac{3}{7}=\frac{31}{140}-\frac{2}{5}\)
\(\frac{x}{4}-\frac{3}{7}=-\frac{5}{28}\)
\(\frac{x}{4}=-\frac{5}{28}+\frac{3}{7}\)
\(\frac{x}{4}=\frac{1}{4}\)
\(\Rightarrow x=1\)
tìm x biết
x-3=(3-x)^2
x^3+3/2x^2+3/4x+1/8=1/64
\(\left(x-3\right)=\left(3-x\right)^2\)
\(\Leftrightarrow x-3=\left(x-3\right)^2\)
\(\Leftrightarrow\left(x-3\right)-\left(x-3\right)^2=0\)
\(\Leftrightarrow\left(x-3\right)\left[1-\left(x-3\right)\right]=0\)
\(\Leftrightarrow\left(x-3\right)\left(4-x\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-3=0\\4-x=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=3\\x=4\end{matrix}\right.\)
___________
\(x^3+\dfrac{3}{2}x^2+\dfrac{3}{4}x+\dfrac{1}{8}=\dfrac{1}{64}\)
\(\Leftrightarrow x^3+3\cdot\dfrac{1}{2}\cdot x^2+3\cdot\left(\dfrac{1}{2}\right)^2\cdot x+\left(\dfrac{1}{2}\right)^3=\dfrac{1}{64}\)
\(\Leftrightarrow\left(x+\dfrac{1}{2}\right)^3=\left(\dfrac{1}{4}\right)^3\)
\(\Leftrightarrow x+\dfrac{1}{2}=\dfrac{1}{4}\)
\(\Leftrightarrow x=\dfrac{1}{4}-\dfrac{1}{2}\)
\(\Leftrightarrow x=-\dfrac{1}{4}\)
tìm 𝑥 biết
x+2/7=-49/(x+2)^2
\(\Leftrightarrow\left(x+2\right)^3=343\)
=>x+2=7
hay x=5
(X-140)^3:7^2=4^5-3^2.4^3.Tìm x
(X-140)^3:7^2=4^5-3^2.4^3.
=>(x - 140)3:72 = 45 - 32.43
(x - 140)3 : 49 = 448
(x - 140)3 = 21952 = 282
x - 140 = 28
x = 168
tìm 2 số x và y biết
x phần 3 = x cộng y = 20
\(\dfrac{x}{3}=x+y=20\Rightarrow x=60\Rightarrow60+y=20\Rightarrow y=-40\)
Ta có:
\(\dfrac{x}{3}=20\)
\(\Rightarrow\)\(x=60\)
Lại có:
\(x+y=20\)
\(\Rightarrow\)\(y=20-60\)
\(\Rightarrow\)\(y=-40\)
Vây x = 60 và y = - 40
\(\dfrac{x}{3}=x+y\)
\(\Leftrightarrow x-\dfrac{1}{3}x=-y\)
\(\Leftrightarrow y=-\dfrac{2}{3}x\)
Ta có: x+y=20
\(\Leftrightarrow x\cdot\dfrac{1}{3}=20\)
hay x=60
=> y=40