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|2x-5|= 3
\(\Rightarrow\orbr{\begin{cases}2x-5=3\\2x-5=-3\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}2x=8\Rightarrow x=4\\2x=2\Rightarrow x=1\end{cases}}\)
Vậy x=4 hoặc =1
-125-(3x+1)=(-2)×(-77)
-125-(3x+1)=154
3x+1=-125-154
3x+1=-279
3x=-279-1
3x=-280
x=\(\frac{-280}{3}\)
Vậy...........................
=> 3A = 1.2. (3-0) +2.3.(4-1) + ...+18.19.(20-17)
=1.2.3-0.1.2+2.3.4-1.2.3+...+18.19.20-17.18.19
=(1.2.3-1.2.3)+(2.3.4-2.3.4)+...+(17.18.19-17.18.19)+18.19.20-0.1.2
=0+0+0+...+0+18.19.20
=18.19.20
=> A = 6.19.20= 114* 20= 2280
`A= 1.2 + 2.3 +3.4 +...+ 18.19`
`3A = 1.2.3 + 2.3.(4-1) + 3.4.(5-2) +....+ 18.19.(20-17)`
`3A = 1.2.3 + 2.3.4 - 1.2.3 + 3.4.5 - 2.3.4 + ....+ 18.19.20 - 17.18.19 `
`3A = 18.19.20`
`A = 6.19.20`
`A = 2280`
a. = 12 + -12 + [-24]
=0+[-24]
=-24
b. = 23 + -23 + 23
=0+23
=23
cho mik nhé
hok tốt
hihi
`A = |6 : 3/5 - 1 1/6 . 6/7| : |4 1/5 . 10/11 + 5 2/11|`
`=|10 - 1| : |42/11 + 57/11|`
`=9 : 9`
`=1`
`7/19*8/11-7/19*(-3)/11+12/19`
`=7/19*(8/11-(-3)/11)+12/19`
`=7/19*1+12/19`
`=7/19+12/19`
`=19/19=1`
a: \(=\left|6\cdot\dfrac{5}{3}-\dfrac{7}{6}\cdot\dfrac{6}{7}\right|:\left|\dfrac{21}{5}\cdot\dfrac{10}{11}+5+\dfrac{2}{11}\right|\)
\(=\left|10-1\right|:\left|\dfrac{42}{11}+\dfrac{2}{11}+5\right|\)
\(=9:9=1\)
b: \(=\dfrac{1}{2}\cdot\dfrac{2}{3}\cdot\dfrac{3}{4}\cdot...\cdot\dfrac{2002}{2003}\cdot\dfrac{2003}{2004}=\dfrac{1}{2004}\)
c: \(=\dfrac{59}{10}\cdot\dfrac{2}{3}-\left|\dfrac{7}{3}\cdot\dfrac{9}{2}-2\cdot\dfrac{7}{3}\right|\cdot\dfrac{4}{7}\)
\(=\dfrac{59}{15}-\dfrac{7}{3}\cdot\dfrac{5}{2}\cdot\dfrac{4}{7}\)
\(=\dfrac{59}{15}-\dfrac{10}{3}=\dfrac{59-50}{15}=\dfrac{9}{15}=\dfrac{3}{5}\)
\(\dfrac{17}{6}+\dfrac{26}{-12}-\dfrac{-13}{39}\)
\(=\dfrac{17}{6}-\dfrac{13}{6}+\dfrac{1}{3}\)
\(=\dfrac{4}{6}+\dfrac{1}{3}\)
\(=\dfrac{2}{3}+\dfrac{1}{3}\)
\(=1\)