23/3 – 9/2
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`a)3/5+(-4/9)`
`=3/5-4/9`
`=27/45-20/45`
`=7/45`
`b)3/5+2/5 . 15/8`
`=3/5 + 30/40`
`=3/5+3/4`
`=12/20+15/20`
`=27/20`
`c)7/2 . 8/13 + 8/13 . (-5/2)`
`=8/13 . (7/2 +(-5)/2)`
`=8/13 . 1`
`=8/13`
`d)-5/17 . (-9/23)+9/23 . (-22/17) + 11 9/23`
`=-5/17 . (-9/23) + 9/23 . (-1) . 22/17 + 11 + 9/23`
`=-5/17 . (-9/23) + (-9/23) . 22/17+11+9/23`
`= -9/23 ( -5/17 + 22/17)+11+9/23`
`= - 9/23 . 1+11+9/23`
`=-9/23+11+9/23`
`=(-9/23+9/23)+11`
`=0+11`
`=11`
a: =27/45-20/45=7/45
b: =3/5+30/40
=3/5+3/4
=12/20+15/20
=27/20
c: =8/13(7/2-5/2+1)=8/13*2=16/13
d: =9/23*5/17-9/23*22/17+11+9/23
=-9/23+11+9/23
=11
\(\text{a)}25\%-\frac{3}{2}+0,5.\frac{12}{5}\)
\(=\frac{1}{4}-\frac{3}{2}+\frac{1}{2}.\frac{12}{5}\)
\(=-\frac{5}{8}+\frac{6}{5}\)
\(=-\frac{25}{40}+\frac{48}{40}\)
\(=\frac{23}{40}\)
\(b)0,25.\frac{7}{3}.30.\text{ }0,5.\frac{8}{45}\)
\(=\frac{1}{4}.\frac{7}{3}.30.\frac{1}{2}.\frac{8}{45}\)
\(=\frac{7}{12}.(30.\frac{8}{90})\)
\(=\frac{7}{12}.\frac{8}{3}\)
\(=\frac{14}{9}\)
\(c)\frac{9}{23}.\frac{5}{8}+\frac{9}{23}.\frac{3}{8}-\frac{9}{23}\)
\(=\frac{9}{23}.\left(\frac{5}{8}+\frac{3}{8}-1\right)\)
\(=\frac{9}{23}.0\)
\(=0\)
#)Giải ;
b) Đặt \(N=1+2+2^2+2^3+...+2^{2012}\)
\(\Rightarrow2N=2+2^2+2^3+2^4+...+2^{2013}\)
\(\Rightarrow2N-N=N=\left(2+2^2+2^3+2^4+...+2^{2013}\right)-\left(1+2+2^2+2^3+...+2^{2012}\right)\)
\(\Rightarrow N=2^{2013}-1\)
Thay N vào M, ta có :
\(M=\frac{2^{2013}-1}{2^{2014}-2}\)
Thêm Cho pen
\(M=\frac{2^{2013}-1}{2^{2014}-2}=\frac{2^{2013}-1}{2.\left(2^{2013}-1\right)}=\frac{1}{2}\)
Phải tính hết nhé
a, \(\left(4\dfrac{1}{9}+3\dfrac{1}{4}\right).2\dfrac{1}{4}+2\dfrac{3}{4}\)
\(=\left(\dfrac{37}{9}+\dfrac{13}{4}\right).\dfrac{9}{4}+\dfrac{11}{4}\)
\(=\dfrac{265}{36}.\dfrac{9}{4}+\dfrac{11}{4}\)
\(=\dfrac{265}{16}+\dfrac{11}{4}\)
\(=\dfrac{309}{16}\)
b, \(\dfrac{9}{23}.\dfrac{5}{8}+\dfrac{9}{23}.\dfrac{3}{8}-\dfrac{9}{23}\)
\(=\dfrac{45}{184}+\dfrac{27}{184}-\dfrac{9}{23}\)
\(=\dfrac{9}{23}-\dfrac{9}{23}\)
\(=\dfrac{1}{1}\)
c, \(1+\left(\dfrac{9}{10}-\dfrac{4}{5}\right)\div3\dfrac{1}{6}\)
\(=1+\left(\dfrac{9}{10}-\dfrac{4}{5}\right)\div\dfrac{19}{6}\)
\(=1+\dfrac{1}{10}\div\dfrac{19}{6}\)
\(=1+\dfrac{3}{95}\)
\(=1\dfrac{3}{95}\)
d, ???
=-85/23-2/7-7/23+9/7
=(-2/7+9/7)+(-85/23-7/23)
=1+(-92/23=-4)
=-3
=
\(-3-\dfrac{16}{23}-\dfrac{2}{7}-\dfrac{7}{23}+\dfrac{9}{7}\)
\(=-3-\left(\dfrac{16}{23}+\dfrac{7}{23}\right)-\left(\dfrac{2}{7}-\dfrac{9}{7}\right)\)
\(=-3-\dfrac{23}{23}-\dfrac{-7}{7}\)
\(=-3-1-\left(-1\right)\)
\(=-3-1+1\)
\(=-3\)
\(\dfrac{23}{3}-\dfrac{9}{2}\)
\(=\dfrac{46}{6}-\dfrac{27}{6}=\dfrac{19}{6}\)
#DatNe
19/6