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\(\dfrac{7}{4}.\dfrac{29}{5}-\dfrac{7}{5}.\dfrac{9}{4}+3\dfrac{2}{15}\) (đổi hỗn số ra phân số)
\(=\) \(\dfrac{7}{4}.\dfrac{29}{5}-\dfrac{7}{5}.\dfrac{9}{4}+\dfrac{47}{15}\) (nhân, chia trước cộng, trừ sau lấy \(\dfrac{7}{4}.\dfrac{29}{5}\)và lấy \(\dfrac{7}{5}.\dfrac{9}{4}\) ra kết quả rồi \(+\dfrac{47}{15}\))
\(=\dfrac{203}{20}-\dfrac{63}{20}+\dfrac{47}{15}\) (cộng, trừ thì cộng, trừ từ trái sang phải)
\(=7+\dfrac{47}{15}=\dfrac{7}{1}+\dfrac{47}{15}\)
\(=\dfrac{105}{15}+\dfrac{47}{15}\)
\(=\dfrac{152}{15}\)
NHỮNG CHỮ IN ĐẬM BẠN KHÔNG CẦN GHI
`@` `\text {Ans}`
`\downarrow`
\(\left(x-\dfrac{1}{5}\right)^2+1=3,5\div7\%\)
`=> (x-1/5)^2 + 1 = 3,5 \div 0,07`
`=> (x-1/5)^2 +1=50`
`=> (x-1/5)^2 = 49`
`=> (x-1/5)^2 = (+-7)^2`
`=>`\(\left[{}\begin{matrix}x-\dfrac{1}{5}=7\\x-\dfrac{1}{5}=-7\end{matrix}\right.\)
`=>`\(\left[{}\begin{matrix}x=7+\dfrac{1}{5}\\x=-7+\dfrac{1}{5}\end{matrix}\right.\)
`=>`\(\left[{}\begin{matrix}x=\dfrac{36}{5}\\x=-\dfrac{34}{5}\end{matrix}\right.\)
Vậy, `x={36/5; -34/5}.`
a: =-5/9-4/9+8/15+7/15-2/11=-2/11
b: =10/17+7/17-5/13-8/13+11/25
=11/25
c: =(9/12-2/12)*3/2=7/12*3/2=21/24=7/8
d: =(31/10-25/10)*3-2
=3/5*3-2
=9/5-2
=-1/5
1)\(\dfrac{2}{9}+\dfrac{-3}{4}+\dfrac{5}{30}\)
\(=\dfrac{2.20}{9.20}+\dfrac{-3.45}{4.45}+\dfrac{5.6}{30.6}\)
\(=\dfrac{40}{180}+\dfrac{-135}{180}+\dfrac{30}{180}\)
\(=\dfrac{40+\left(-135\right)+30}{180}\)
\(=\dfrac{-65}{180}\)
\(=\dfrac{-13}{36}\)
2)\(\dfrac{-7}{12}-\dfrac{11}{18}\)
\(=\dfrac{-7.3}{12.3}-\dfrac{11.2}{18.2}\)
\(=\dfrac{-21}{36}-\dfrac{22}{36}\)
\(=\dfrac{-21-22}{36}\)
\(=\dfrac{-43}{36}\)
3)\(\dfrac{7}{8}-\dfrac{-5}{16}\)
\(=\dfrac{7.2}{8.2}-\dfrac{-5}{16}\)
\(=\dfrac{14}{16}-\dfrac{-5}{16}\)
\(=\dfrac{14-\left(-5\right)}{16}\)
\(=\dfrac{19}{16}\)
4)\(\dfrac{3}{8}-\dfrac{-9}{10}-\dfrac{5}{16}\)
\(=\dfrac{3.10}{8.10}-\dfrac{-9.8}{10.8}-\dfrac{5.5}{16.5}\)
\(=\dfrac{30}{80}-\dfrac{-72}{80}-\dfrac{25}{80}\)
\(=\dfrac{30-\left(-72\right)-25}{80}\)
\(=\dfrac{77}{80}\)
\(C=\dfrac{-5}{7}+\dfrac{-2}{7}+\dfrac{3}{4}+\dfrac{1}{4}+\dfrac{-1}{5}=-1+1-\dfrac{1}{5}=\dfrac{-1}{5}\)
a) \(\left(\frac{-1}{2}\right)+\left|\frac{-7}{6}\right|+\left(\frac{-7}{8}\right)=\frac{-1}{2}+\frac{7}{6}+\left(\frac{-7}{8}\right)=\frac{-5}{24}\)
b) \(\frac{3}{2}.\left|2+x\right|=\frac{5}{4}\)
\(\Rightarrow\left|2+x\right|=\frac{5}{4}:\frac{3}{2}=\frac{5}{6}\)
\(\Rightarrow2+x=\pm\frac{5}{6}\)
\(\Rightarrow\orbr{\begin{cases}2+x=\frac{5}{6}\Rightarrow x=\frac{5}{6}-2=\frac{-7}{6}\\2+x=\frac{-5}{6}\Rightarrow x=\frac{-5}{6}-2=\frac{-17}{6}\end{cases}}\)
Vậy \(x=\left\{\frac{-7}{6};\frac{-17}{6}\right\}\)
c) Ta có: \(\frac{3,7}{x}=\frac{-5}{1,2}\Rightarrow3,7.1,2:\left(-5\right)=x\)
\(\Rightarrow x=-0,888\)
d) Tự làm
A=(\(\frac{-1}{2}\))+|\(\frac{-7}{6}\)|+(\(\frac{-7}{8}\))
=(\(\frac{-1}{2}\))+\(\frac{-7}{6}\)+(\(\frac{-7}{8}\))
=\(\frac{2}{3}\)+(\(\frac{-7}{8}\))
=\(\frac{-5}{24}\)
Vậy x=\(\frac{-5}{24}\)
B=\(\frac{3}{2}\)x|2+x|=\(\frac{5}{4}\)
=|2+x|=\(\frac{5}{4}\):\(\frac{3}{2}\)
=\(\orbr{\begin{cases}2+x=\frac{5}{6}\\2+x=\frac{-5}{6}\end{cases}}\)
=\(\orbr{\begin{cases}x=\frac{5}{6}-2\\x=\frac{-5}{6}-2\end{cases}}\)
=\(\orbr{\begin{cases}x=-1\frac{1}{6}\\x=-2\frac{5}{6}\end{cases}}\)
Vậy x\(\in\){\(-1\frac{1}{6}\);\(-2\frac{5}{6}\)}
\(a.\dfrac{3}{2}+\dfrac{-1}{3}< \dfrac{x}{6}< \dfrac{1}{9}+\dfrac{31}{18}\)
\(\Leftrightarrow\dfrac{7}{6}< \dfrac{x}{6}< \dfrac{11}{6}\)
\(\Leftrightarrow7< x< 11\)
\(\Leftrightarrow x\in\left\{8;9;10\right\}\)
\(b.\dfrac{-5}{12}+\dfrac{7}{12}+\dfrac{-1}{12}< \dfrac{x}{12}< \dfrac{2}{15}+\dfrac{1}{5}\)
\(\Leftrightarrow\dfrac{1}{12}< \dfrac{x}{12}< \dfrac{1}{3}\)
\(\Leftrightarrow\dfrac{1}{12}< \dfrac{x}{12}< \dfrac{4}{12}\)
\(\Leftrightarrow1< x< 4\)
\(\Leftrightarrow x\in\left\{2;3\right\}\)
\(2\left[3-9\cdot\left(-3\right)+2\left(5-7\right)\right]-18:\left(-3\right)^2\)
\(=2\left[3+27+2\cdot\left(-2\right)\right]-18:9\)
\(=2\left[30-4\right]-2\)
\(=2\cdot26-2=50\)
=2.(3-9.-3 +2.-2)-18:(-3)2
=2.(3--27+-4)-18:-9
=2.(30+-4) -18:-9
=2.26-18:-9
=52--2
=54