\(5x^2\) - \(\dfrac{5}{3}\)\(x\) \(=0\)
Help Mee
\(5x^2\) - \(\dfrac{5}{3}\)\(x\) \(=0\)
Help Mee
\(5x^2-\dfrac{5}{3}x=0\\ x\left(5x-\dfrac{5}{3}\right)=0\\ \left[{}\begin{matrix}x=0\\5x-\dfrac{5}{3}=0\end{matrix}\right.=>\left[{}\begin{matrix}x=0\\x=\dfrac{5}{3}:5\end{matrix}\right.=>\left[{}\begin{matrix}x=0\\x=\dfrac{1}{3}\end{matrix}\right.\)
\(=-\dfrac{7}{19}\left(\dfrac{8}{11}+\dfrac{3}{11}\right)-\dfrac{12}{19}\\ =\dfrac{-7}{19}.\dfrac{11}{11}-\dfrac{12}{19}\\ =-\dfrac{7}{19}-\dfrac{12}{19}\\ =\dfrac{-7-12}{19}\\ =\dfrac{-19}{19}=-1\)
\(\dfrac{-7}{19}\cdot\dfrac{8}{11}-\dfrac{7}{19}\cdot\dfrac{3}{11}-\dfrac{12}{19}\)
\(=-\dfrac{7}{19}\cdot\left(\dfrac{8}{11}+\dfrac{3}{11}\right)-\dfrac{12}{19}\)
\(=-\dfrac{7}{19}\cdot1-\dfrac{12}{19}\)
\(=-\dfrac{19}{19}=-1\)
\(\dfrac{-7}{19}.\dfrac{8}{11}-\dfrac{7}{19}.\dfrac{3}{11}-\dfrac{12}{19}=\dfrac{-7}{19}\left(\dfrac{8}{11}+\dfrac{3}{11}\right)-\dfrac{12}{19}=\dfrac{-7}{19}.1-\dfrac{12}{19}=-1\)
=>1/5x+5/6x-1,75=-17/30
=>31/30x=71/60
=>x=71/62
\(4x+\dfrac{5}{7}x-4x=-\dfrac{15}{7}\\ \dfrac{5}{7}x=-\dfrac{15}{7}\\ x=-3\)
\(\left(5+2x^2\right)\left(x+\dfrac{17}{21}\right)=0\)
\(\Rightarrow x+\dfrac{17}{21}=0\) (do \(5+2x^2>0\))
\(\Rightarrow x=-\dfrac{17}{21}\)
\(=\dfrac{1}{5}\left(\dfrac{5}{4\cdot9}+\dfrac{5}{9\cdot14}+...+\dfrac{5}{44\cdot49}\right)\cdot\dfrac{-7}{1}\)
\(=\dfrac{-7}{5}\left(\dfrac{1}{4}-\dfrac{1}{9}+\dfrac{1}{9}-\dfrac{1}{14}+...+\dfrac{1}{44}-\dfrac{1}{49}\right)\)
\(=\dfrac{-7}{5}\cdot\dfrac{45}{196}=-\dfrac{9}{28}\)
Tìm x , biết: x∈Z và :
`(-3)/2 + 5/7 +(-31)/14 ≤x≤ 1/2+1/3+1/6`
`-3/2+5/7-31/14≤x≤1/2+1/3+1/6`
`-21/14+10/14-31/14≤x≤3/6+2/6+1/6`
`(-21+10-31)/14 ≤ x≤ (3+2+1)/6`
`-42/14 ≤ x ≤ x 6/6`
`-3 ≤ x ≤ 1`
`=> x = {-3;-2;-1;0;1}`
`-3/2 + 5/7 + (-31/14)=-21/7 + 10/14 + (-31/14) = (-21+10+(-31))/14=-42/14=-3`
`1/2 + 1/3 + 1/6= 3/6 + 2/6 + 1/6=(3+2+1)/6=6/6=1`
mà `-3 <= x <= 1`
`=>x= 1;0;-1;-2;-3`
ta có :
`4/5 -5/6= 24/30 - 25/30=-1/30`
`1/3 - 3/10 = 10/30 - 9/30=1/30`
mà `-1/30 <= x/30 <= 1/30`
`=>x= -1;0;1`
`4/5-5/6≤ x/30 ≤ 1/3 - 3/10`
`24/30 - 25/30 ≤ x/30 ≤10/30 - 9/30`
`-1/30 ≤ x/30 ≤ 1/30`
`-1≤x≤1`
`=> x∈ {-1;0;1}`
\(-\dfrac{1}{30}\le\dfrac{x}{30}\le\dfrac{1}{30}\Rightarrow-1\le x\le1\Rightarrow x=-1;0;1\)
=>1+x-9/5=10/12-7/12=1/4
=>x-4/5=1/4
=>x=1/4+4/5=0,25+0,8=1,05
21: \(=1-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{7}+...+\dfrac{1}{97}-\dfrac{1}{100}\)
=99/100
22: \(=1-\dfrac{1}{2}+1-\dfrac{1}{6}+...+1-\dfrac{1}{90}\)
\(=9-\left(1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+...+\dfrac{1}{9}-\dfrac{1}{10}\right)\)
\(=8+\dfrac{1}{10}=8.1\)
21. \(\dfrac{3}{1.4}+\dfrac{3}{4.7}+...+\dfrac{3}{97.100}\)
\(=\dfrac{4-1}{1.4}+\dfrac{7-4}{4.7}+...+\dfrac{100-97}{97.100}\)
\(=1-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{7}+...+\dfrac{1}{97}-\dfrac{1}{100}\)
\(=1-\dfrac{1}{100}\)
\(=\dfrac{99}{100}\)
22. https://hoc24.vn/cau-hoi/.6655902032768