Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
Phá ngoặc ra rồi tính ! Bài này thằng rốt nhất lớp tôi cx bt lm
\(\dfrac{x}{2}-\left(\dfrac{3x}{5}-\dfrac{13}{5}\right)=\left(\dfrac{7}{5}+\dfrac{7}{10}x\right)\)
\(\Rightarrow\dfrac{x}{2}-\dfrac{3x}{5}+\dfrac{13}{5}=\dfrac{7}{5}+\dfrac{7x}{10}\)
\(\Rightarrow\dfrac{x}{2}-\dfrac{3x}{5}-\dfrac{7x}{10}=\dfrac{7}{5}-\dfrac{13}{5}\)
\(\Rightarrow\dfrac{5x}{10}-\dfrac{6x}{10}-\dfrac{7x}{10}=-\dfrac{6}{5}\)
\(\Rightarrow\dfrac{-4x}{5}=-\dfrac{6}{5}\)
\(\Rightarrow-4x=-6\)
\(\Rightarrow x=\dfrac{3}{2}\)
Mấy bài dễ tự làm nhé:D
1)
Đặt: \(\dfrac{a}{b}=\dfrac{c}{d}=k\Leftrightarrow\left\{{}\begin{matrix}a=bk\\c=dk\end{matrix}\right.\)
\(\left\{{}\begin{matrix}\dfrac{a}{a+b}=\dfrac{bk}{bk+b}=\dfrac{bk}{b\left(k+1\right)}=\dfrac{k}{k+1}\\\dfrac{c}{c+d}=\dfrac{dk}{dk+d}=\dfrac{dk}{d\left(k+1\right)}=\dfrac{k}{k+1}\end{matrix}\right.\)
Ta có điều phải chứng minh
\(\left\{{}\begin{matrix}\dfrac{a}{a-b}=\dfrac{bk}{bk-b}=\dfrac{bk}{b\left(k-1\right)}=\dfrac{k}{k-1}\\\dfrac{c}{c-d}=\dfrac{dk}{dk-d}=\dfrac{dk}{d\left(k-1\right)}=\dfrac{k}{k-1}\end{matrix}\right.\)
Ta có điều phải chứng minh
1: \(\Leftrightarrow3x+4=2\)
=>3x=-2
=>x=-2/3
2: \(\Leftrightarrow7x-7=6x-30\)
=>x=-23
3: =>\(5x-5=3x+9\)
=>2x=14
=>x=7
4: =>9x+15=14x+7
=>-5x=-8
=>x=8/5
\(\dfrac{2}{3x}\)-\(\dfrac{3}{12}\)= \(\dfrac{4}{5}\)-\(\left(\dfrac{7}{x}-2\right)\)
\(\dfrac{2}{3x}-\dfrac{1}{4}=\dfrac{4}{5}-\dfrac{7}{x}+2\)
\(\dfrac{2}{3x}+\dfrac{7}{x}=\dfrac{4}{5}+\dfrac{1}{4}+2\)
\(\dfrac{2x}{3x^2}+\dfrac{21x}{3x^2}=\dfrac{61}{20}\)
\(\dfrac{2x+21x}{3x^2}=\dfrac{61}{20}\)
=> 20(2x + 21x)= 61.3x\(^2\)
=> 40x + 420x= 183x\(^2\)
=>460x = 183x\(^2\)
=> \(\dfrac{460}{183}\)= \(\dfrac{x^2}{x}\)
=> x=\(\dfrac{460}{183}\)
a: =>4x-6-9=5-3x-3
=>4x-15=-3x+2
=>7x=17
hay x=17/7
b: \(\Leftrightarrow\dfrac{2}{3x}-\dfrac{1}{4}=\dfrac{4}{5}-\dfrac{7}{x}+2\)
=>2/3x+21/3x=4/5+2+1/4=61/20
=>23/3x=61/20
=>3x=23:61/20=460/61
hay x=460/183
3. Từ \(\dfrac{x-2}{27}=\dfrac{3}{x-2}\Rightarrow\left(x-2\right)^2=81\)
\(\Rightarrow\left(x-2\right)^2=\left(\pm9\right)^2\\ \Rightarrow\left[{}\begin{matrix}x-2=-9\\x-2=9\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=-7\\x=11\end{matrix}\right.\)
Vậy x = -7 hoặc x = 11
4. Từ \(\dfrac{2x+5}{9-2x}=\dfrac{2}{5}\)
\(\Rightarrow5\left(2x+5\right)=2\left(9-2x\right)\\ \Leftrightarrow10x+25=18-4x\\ \Leftrightarrow14x=-7\\ \Rightarrow x=-\dfrac{1}{2}\)
5. Từ \(\dfrac{x-7}{x+8}=\dfrac{x-8}{x+9}\)
\(\Rightarrow\left(x-7\right)\left(x+9\right)=\left(x-8\right)\left(x+8\right)\\ \Leftrightarrow x^2+2x-63=x^2-64\\ \Leftrightarrow2x=-1\\ \Rightarrow x=-\dfrac{1}{2}\)
=1/8-1/5+1/7*3/8-3/5+3/7 + 1/2+1/3-1/5*3/4+1/2-3/10
=19/280*57/280+19/30*19/20
=19/280.280/57+19/30.20/19
=1/1.1/3+1/3.2/1
=1/3+2/3=3/3
=1
\(\dfrac{72-x}{7}=\dfrac{x-4}{9}\)
\(\Rightarrow9\left(72-x\right)=7\left(x-4\right)\)
\(\Rightarrow648-9x=2x-28\)
\(\Rightarrow11x-28=648\)
\(\Rightarrow11x=676\Rightarrow x=\dfrac{676}{11}\)
\(\dfrac{37-x}{x+13}=\dfrac{3}{7}\)
\(\Rightarrow7\left(37-x\right)=3\left(x+13\right)\)
\(\Rightarrow259-7x=3x+39\)
\(\Rightarrow10x+39=259\)
\(\Rightarrow10x=220\Rightarrow x=22\)
\(\dfrac{x+4}{20}=\dfrac{5}{x+4}\)
\(\Rightarrow\left(x+4\right)^2=100\)
\(\Rightarrow\left(x+4\right)^2=\pm10^2\)
\(\Rightarrow\left[{}\begin{matrix}x+4=10\Rightarrow x=6\\x+4=-10\Rightarrow x=-14\end{matrix}\right.\)
\(\dfrac{x-1}{x+2}=\dfrac{x-2}{x+3}\)
\(\Rightarrow\left(x-1\right)\left(x+3\right)=\left(x-2\right)\left(x+2\right)\)
\(\Rightarrow x\left(x+3\right)-1\left(x+3\right)=x\left(x+2\right)-2\left(x+2\right)\)
\(\Rightarrow x^2+3x-x-3=x^2+2x-2x-4\)
\(\Rightarrow x^2+2x-3=x^2-4\)
\(\Rightarrow2x-3=-4\)
\(\Rightarrow2x=-1\)
\(\Rightarrow x=-\dfrac{1}{2}\)
Giải:
a) \(1\dfrac{2}{5}x+\dfrac{4}{5}=-\dfrac{7}{10}\)
\(\Leftrightarrow\dfrac{7}{5}x+\dfrac{4}{5}=-\dfrac{7}{10}\)
\(\Leftrightarrow\dfrac{7}{5}x=-\dfrac{7}{10}-\dfrac{4}{5}\)
\(\Leftrightarrow\dfrac{7}{5}x=-\dfrac{3}{2}\)
\(\Leftrightarrow x=-\dfrac{3}{2}:\dfrac{7}{5}=-\dfrac{15}{14}\)
Vậy ...
b) \(5-3x=2\dfrac{2}{7}\)
\(\Leftrightarrow5-3x=\dfrac{16}{7}\)
\(\Leftrightarrow3x=5-\dfrac{16}{7}\)
\(\Leftrightarrow3x=\dfrac{19}{7}\)
\(\Leftrightarrow x=\dfrac{19}{7}:3=\dfrac{19}{21}\)
Vậy ...
=>1/2x-3/5x+13/5=7/5+7/10x
=>-1/10x-7/10x=7/5-13/5
=>-4/5x=-6/5
=>x=6/5:4/5=6/5x5/4=6/4=1,5