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\(a,\dfrac{2}{5}-\dfrac{3}{8}+\dfrac{7}{6}=\dfrac{16}{40}-\dfrac{15}{40}+\dfrac{7}{6}=\dfrac{1}{40}+\dfrac{7}{6}=\dfrac{3}{120}+\dfrac{140}{120}=\dfrac{143}{120}\)
\(b,\dfrac{2}{3}+\left[\dfrac{5}{7}+\left(-\dfrac{2}{3}\right)\right]=\dfrac{2}{3}+\dfrac{5}{7}+\left(-\dfrac{2}{3}\right)=\left[\dfrac{2}{3}+\left(-\dfrac{2}{3}\right)\right]+\dfrac{5}{7}=0+\dfrac{5}{7}=\dfrac{5}{7}\)
\(c,\dfrac{5}{13}+\left(-\dfrac{5}{7}\right)+\left(-\dfrac{20}{41}\right)+\dfrac{8}{13}+\left(-\dfrac{21}{41}\right)\)
\(=\left(\dfrac{5}{13}+\dfrac{8}{13}\right)-\dfrac{5}{7}-\dfrac{20}{41}-\dfrac{21}{41}=-\dfrac{5}{7}\)
a: =48/120-45/120+140/120
=143/120
b: =2/3-2/3+5/7=5/7
c: =5/13+8/13-5/7-20/41-21/41
=-5/7
đúng ko?
1: =5/13+8/13-20/41-21/41-5/17
=1-1-5/17=-5/17
2: =1/5+4/5-2/9-7/9+16/17
=16/17+1-1=16/17
3: =1/3-1/5+1/5-1/7+...+1/99-1/101
=1/3-1/101
=98/303
p) \(\frac{-5}{9}+\frac{8}{15}+\frac{-2}{11}+\frac{4}{-9}+\frac{7}{15}\)
\(=\left(\frac{-5}{9}+\frac{-4}{9}\right)+\left(\frac{8}{15}+\frac{7}{15}\right)+\frac{-2}{11}\)
\(=-1+1+\frac{-2}{11}\)
\(=-\frac{2}{11}\)
q) \(\frac{5}{13}+\frac{-5}{17}+\frac{-20}{41}+\frac{8}{13}+\frac{-21}{41}\)
\(=\left(\frac{5}{13}+\frac{8}{13}\right)+\left(\frac{-20}{41}+\frac{-21}{41}\right)+\frac{-5}{17}\)
\(=1+\left(-1\right)+\frac{-5}{17}=\frac{-5}{17}\)
r) \(\frac{1}{5}+\frac{-2}{9}+\frac{-7}{9}+\frac{4}{5}+\frac{16}{17}\)
\(=\left(\frac{1}{5}+\frac{4}{5}\right)+\left(\frac{-2}{9}+\frac{-7}{9}\right)+\frac{16}{17}\)
\(=1+\left(-1\right)+\frac{16}{17}=\frac{16}{17}\)
a: =35/17-18/17-9/5+4/5
=1-1=0
b: =-7/19(3/17+8/11-1)
=7/19*18/187=126/3553
c: =26/15-11/15-17/3-6/13
=1-6/13-17/3
=7/13-17/3=-200/39
1.a) (-4).36+(-4).64 = (-4).(36+64) = (-4).100 = -400
b) \(\frac{-4}{17}+\left(\frac{2}{3}+\frac{4}{17}\right)\)
\(=\frac{-4}{17}+\frac{2}{3}+\frac{4}{17}\)
\(=\left(\frac{-4}{17}+\frac{4}{17}\right)+\frac{2}{3}\)
\(=0+\frac{2}{3}=\frac{2}{3}\)
c) \(\frac{5}{13}+\frac{-5}{7}+\frac{-20}{41}+\frac{8}{13}+\frac{-21}{41}\)
\(=\left(\frac{5}{13}+\frac{8}{13}\right)+\left(\frac{-20}{41}+\frac{-21}{41}\right)+\frac{-5}{7}\)
\(1+\left(-1\right)+\frac{-5}{7}=0+\frac{-5}{7}=\frac{-5}{7}\)
Học tốt .