Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
a)\(\) Ta có : x / 3,15 = 0,15 / 7,2
(=) x = 0,15 . 3,15 / 7,2
= 21 / 320
b) Ta có : -2,6 / x = -12 / 42
(=) x = -2,6 . 42 / -12
= 91 / 10
\(2x\left(x-\frac{2}{3}\right)=0\)
\(\Rightarrow\orbr{\begin{cases}2x=0\\x-\frac{2}{3}=0\end{cases}\Rightarrow\orbr{\begin{cases}x=0\\x=\frac{2}{3}\end{cases}}}\)
\(\frac{37-x}{x+13}=\frac{3}{7}\)
\(\left(37-x\right).7=\left(x+13\right).3\)
\(259-x7=x3+39\)
\(x7-x3=39-259\)
\(x4=-220\Leftrightarrow x=-55\)
a)\(\frac{x}{3,15}=\frac{0,15}{7,2}\)
\(\Rightarrow7,2x=3,15.0,15\)
\(7,2x=0,4725\)
x = 0,4725:7,2
x=0,065625
b) \(2x\left(x-\frac{2}{3}\right)=0\)
\(\Rightarrow\orbr{\begin{cases}2x=0\\x-\frac{2}{3}=0\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=0:2=0\\x=0+\frac{2}{3}=\frac{2}{3}\end{cases}}\)
Vậy........................................
\(c)\frac{37-x}{x+13}=\frac{3}{7}\)
\(\Rightarrow\left(37-x\right)7=3\left(x+13\right)\)
259-7x=3x+39
-7x-3x=39-259
-10x=-220
x=-220:(-10)
x=22
a) \(\frac{-3}{5}.y=\frac{21}{10}\)
\(y=\frac{21}{10}:\frac{-3}{5}\)
\(y=\frac{-7}{2}\)
vậy \(y=\frac{-7}{2}\)
b) \(y:\frac{3}{8}=-1\frac{31}{33}\)
\(y:\frac{3}{8}=\frac{-64}{33}\)
\(y=\frac{-64}{33}.\frac{3}{8}\)
\(y=\frac{-8}{11}\)
vậy \(y=\frac{-8}{11}\)
c) \(1\frac{2}{5}.y+\frac{3}{7}=\frac{-4}{5}\)
\(\frac{7}{5}.y+\frac{3}{7}=\frac{-4}{5}\)
\(\frac{7}{5}.y=\frac{-4}{5}-\frac{3}{7}\)
\(\frac{7}{5}.y=\frac{-43}{35}\)
\(y=\frac{-43}{35}:\frac{7}{5}\)
\(y=\frac{-43}{49}\)
vậy \(y=\frac{-43}{49}\)
d) \(\frac{-11}{12}.y+0,25=\frac{5}{6}\)
\(\frac{-11}{12}.y=\frac{5}{6}-0,25\)
\(\frac{-11}{12}.y=\frac{7}{12}\)
\(y=\frac{7}{12}:\frac{-11}{12}\)
\(y=\frac{-7}{11}\)
vậy \(y=\frac{-7}{11}\)
a) \(\frac{1}{2}-|\frac{5}{4}-2x|=\frac{1}{3}\Leftrightarrow|\frac{5}{4}-2x|=\frac{1}{2}-\frac{1}{3}=\frac{1}{6}\)
\(\Leftrightarrow\orbr{\begin{cases}\frac{5}{4}-2x=\frac{1}{6}\\\frac{5}{4}-2x=-\frac{1}{6}\end{cases}\Leftrightarrow\orbr{\begin{cases}2x=\frac{5}{4}-\frac{1}{6}=\frac{13}{12}\\2x=\frac{5}{4}+\frac{1}{6}=\frac{17}{12}\end{cases}}}\)
Tự làm nốt và kết luận
b) \(\frac{x+1}{10}+\frac{x+1}{11}+\frac{x+1}{12}=\frac{x+1}{13}+\frac{x+1}{14}\)
\(\Leftrightarrow\frac{x+1}{10}+\frac{x+1}{11}+\frac{x+1}{12}-\frac{x+1}{13}-\frac{x+1}{14}=0\)
\(\Leftrightarrow\left(x+1\right)\left(\frac{1}{10}+\frac{1}{11}+\frac{1}{12}-\frac{1}{13}+\frac{1}{14}\right)=0\)
Vì \(\left(\frac{1}{10}+\frac{1}{11}+\frac{1}{12}-\frac{1}{13}+\frac{1}{14}\right)\ne0\forall x\Rightarrow x+1=0\Leftrightarrow x=-1\)
Vậy ....
#)Giải :
a) x + 2x + 3x + ... + 100x = - 213
=> 100x + ( 2 + 3 + 4 + ... + 100 ) = - 213
=> 100x + 5049 = - 213
<=> 100x = - 5262
<=> x = - 52,62
#)Giải :
b) \(\frac{1}{2}x-\frac{1}{3}=\frac{1}{4}x-\frac{1}{6}\)
\(\Rightarrow\frac{1}{2}x+\frac{1}{4}x=\frac{1}{3}+\frac{1}{6}\)
\(\Rightarrow\frac{1}{2}x+\frac{1}{4}x=\frac{1}{2}\)
\(\Rightarrow\left(\frac{1}{2}+\frac{1}{4}\right)x=\frac{1}{2}\)
\(\Rightarrow\frac{3}{4}x=\frac{1}{2}\)
\(\Leftrightarrow x=\frac{2}{3}\)
\(a)\frac{3}{4}+\frac{2}{5}x=\frac{29}{60}\)
\(\)TỰ LÀM NHA HIHI
MI SUỐT NGÀY NGỒI MÁY TÍNH LƯỚT FACE, LÚC NÀO ĐI QUA CŨNG THẤY
d) \(\frac{x+1}{2009}+\frac{x+2}{2008}+\frac{x+3}{2007}=\frac{x+10}{2000}+\frac{x+11}{1999}+\frac{x+12}{1998}\)
<=> \(\frac{x+1}{2009}+\frac{x+2}{2008}+\frac{x+3}{2007}-\frac{x+10}{2000}-\frac{x+11}{1999}-\frac{x+12}{1998}=0\)
<=> \(\left(\frac{x+1}{2009}+1\right)+\left(\frac{x+2}{2008}+1\right)+\left(\frac{x+3}{2007}+1\right)-\left(\frac{x+10}{2000}+1\right)-\left(\frac{x+11}{1999}+1\right)-\left(\frac{x+12}{1998}+1=0\right)\)
<=> \(\frac{x+2010}{2009}+\frac{x+2010}{2008}+\frac{x+2010}{2007}-\frac{x+2010}{2000}-\frac{x+2010}{1999}-\frac{x+2010}{1998}=0\)
<=>\(\left(x+2010\right).\left(\frac{1}{2009}+\frac{1}{2008}+\frac{1}{2007}-\frac{1}{2000}-\frac{1}{1999}-\frac{1}{1998}\right)=0\)
<=> x+2010 = 0 vì \(\frac{1}{2009}+\frac{1}{2008}+\frac{1}{2007}-\frac{1}{2000}-\frac{1}{1999}-\frac{1}{1998}\ne0\)
<=> x = -2010
\(a.\) \(\frac{x}{3.15}\) \(=\) \(\frac{0.15}{7.2}\)
<=> \(x=\) \(\frac{0.15\cdot3.15}{7.2}\)
<=>\(x=0.065625\)
\(b.\) \(\frac{-2.6}{x-11}=\frac{-12}{42}\)
<=>\(x-11=\frac{-2.6\cdot-12}{42}\)
<=>\(x-11=0.742857142\)
<=>\(x=11.74285714\)
\(3\frac{4}{5}:2x=0,25:2\frac{2}{3}\)
\(\Leftrightarrow\frac{19}{5}:2x=0,25:\frac{8}{3}\)
\(\Leftrightarrow\frac{19}{5}:2x=0,25\cdot\frac{3}{8}\)
\(\Leftrightarrow\frac{19}{5}:2x=\frac{3}{32}\)
\(\Leftrightarrow2x=\frac{19}{5}:\frac{3}{32}=\frac{19}{5}\cdot\frac{32}{3}=\frac{608}{15}\)
\(\Leftrightarrow x=\frac{608}{15}:2=\frac{608}{30}=\frac{304}{15}\)