2*a+3*c/2*b+3*d=2*a-3*c/2*b-3*c
giúp mình với!!! thanks nhìu
K
Khách
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
Những câu hỏi liên quan
PH
1
NN
Nguyễn Ngọc Anh Minh
CTVHS
VIP
10 tháng 10 2015
Ta có
\(\frac{a}{2}=\frac{2b}{3}=\frac{3c}{4}\left(1\right)\Rightarrow3a=4b\left(2\right)\)
Ta có a-b=15 => a=15+b thay vào 2 => b=45 => a=15+45=60 thay a=60 vào (1) => c=40
8 tháng 12 2016
Từ \(\left(a+b+c\right)^2=a^2+b^2+c^2+2ab+2ac+2bc\)
Mà \(\left(a+b+c\right)^2=a^2+b^2+c^2\)
\(\Rightarrow2ab+2ac+2bc=0\)
\(\Rightarrow2\left(ab+ac+bc\right)=0\)
\(\Rightarrow ab+ac+bc=0\)
\(\Leftrightarrow\frac{1}{a}+\frac{1}{b}+\frac{1}{c}=0\Leftrightarrow\frac{1}{a}=-\left(\frac{1}{b}+\frac{1}{c}\right)\). Khi đó
\(\frac{1}{a^3}+\frac{1}{b^3}+\frac{1}{c^3}=\frac{1}{b^3}+\frac{1}{c^3}-\left(\frac{1}{b}+\frac{1}{c}\right)^3=-\frac{3}{bc}\left(\frac{1}{b}+\frac{1}{c}\right)=-\frac{3}{bc}\cdot\frac{-1}{a}=\frac{3}{abc}\)
23 tháng 7 2023
`@` `\text {Ans}`
`\downarrow`
`a)`
\(\dfrac{7}{5}\cdot\dfrac{8}{19}+\dfrac{7}{5}\cdot\dfrac{12}{19}-\dfrac{7}{5}\cdot\dfrac{1}{19}\)
`=`\(\dfrac{7}{5}\cdot\left(\dfrac{8}{19}+\dfrac{12}{19}-\dfrac{1}{19}\right)\)
`=`\(\dfrac{7}{5}\cdot\dfrac{19}{19}=\dfrac{7}{5}\cdot1=\dfrac{7}{5}\)
`b)`
\(-\dfrac{3}{5}\cdot\dfrac{5}{7}+\left(-\dfrac{3}{5}\right)\cdot\dfrac{3}{7}+\left(-\dfrac{3}{5}\right)\cdot\dfrac{6}{7}\)
`=`\(-\dfrac{3}{5}\cdot\left(\dfrac{5}{7}+\dfrac{3}{7}+\dfrac{6}{7}\right)\)
`=`\(-\dfrac{3}{5}\cdot\dfrac{14}{7}\)
`=`\(-\dfrac{3}{5}\cdot2=-\dfrac{6}{5}\)
`c)`
\(10\dfrac{2}{9}+\left(2\dfrac{2}{5}-7\dfrac{2}{9}\right)\)
`=`\(10\dfrac{2}{9}+2\dfrac{2}{5}-7\dfrac{2}{9}\)
`=`\(\left(10\dfrac{2}{9}-7\dfrac{2}{9}\right)+2\dfrac{2}{5}\)
`=`\(3+2\dfrac{2}{5}=\dfrac{27}{5}\)
`d)`
\(6\dfrac{3}{10}-\left(3\dfrac{4}{7}+2\dfrac{3}{10}\right)\)
`=`\(6\dfrac{3}{10}-3\dfrac{4}{7}-2\dfrac{3}{10}\)
`=`\(\left(6\dfrac{3}{10}-2\dfrac{3}{10}\right)-3\dfrac{4}{7}\)
`=`\(4-3\dfrac{4}{7}=\dfrac{3}{7}\)
VN
Võ Ngọc Phương
VIP
23 tháng 7 2023
a) \(\dfrac{7}{5}.\dfrac{8}{19}+\dfrac{7}{5}.\dfrac{12}{19}-\dfrac{7}{5}.\dfrac{1}{19}\)
\(=\dfrac{7}{5}.\left(\dfrac{8}{19}+\dfrac{12}{19}-\dfrac{1}{19}\right)\)
\(=\dfrac{7}{5}.1\)
\(=\dfrac{7}{5}\)
b) \(\dfrac{-3}{5}.\dfrac{5}{7}+\dfrac{-3}{5}.\dfrac{3}{7}+\dfrac{-3}{5}.\dfrac{6}{7}\)
\(=\dfrac{-3}{5}.\left(\dfrac{5}{7}+\dfrac{3}{7}+\dfrac{6}{7}\right)\)
\(=\dfrac{-3}{5}.2\)
\(=\dfrac{-6}{5}\)
c) \(10\dfrac{2}{9}+\left(2\dfrac{2}{5}-7\dfrac{2}{9}\right)\)
\(=\dfrac{92}{9}+\dfrac{12}{5}-\dfrac{65}{9}\)
\(=\dfrac{92}{9}-\dfrac{65}{9}+\dfrac{12}{5}\)
\(=3+\dfrac{12}{5}\)
\(=\dfrac{15}{5}+\dfrac{12}{5}\)
\(=\dfrac{27}{5}\)
d) \(6\dfrac{3}{10}-\left(3\dfrac{4}{7}+2\dfrac{3}{10}\right)\)
\(=\dfrac{63}{10}-\dfrac{25}{7}-\dfrac{23}{10}\)
\(=\dfrac{63}{10}-\dfrac{23}{10}-\dfrac{25}{7}\)
\(=4-\dfrac{25}{7}\)
\(=\dfrac{28}{7}-\dfrac{25}{7}\)
\(=\dfrac{3}{7}\)
Chúc bạn học tốt
AO
2 tháng 2 2018
a) \(-15\left(x-2\right)+7\left(3-x\right)=7\)
\(-15x+30+21-7x=7\)
\(-22x+51=7\)
\(-22x=-44\)
\(x=2\)
vậy \(x=2\)
AO
2 tháng 2 2018
b) \(\left(x-5\right)\left(x-7\right)< 0\)
\(\Rightarrow\hept{\begin{cases}x-5< 0\\x-7>0\end{cases}}\) hoặc \(\hept{\begin{cases}x-5>0\\x-7< 0\end{cases}}\)
\(\Rightarrow\hept{\begin{cases}x< 5\\x>7\end{cases}}\) hoặc \(\hept{\begin{cases}x>5\\x< 7\end{cases}}\)
\(\Rightarrow5< x< 7\)
\(\Rightarrow x=6\)