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a) 5/9 + 4/9 . 3/7 + 4/9 . 4/7
= 5/9 + 4/9 . (3/7 + 4/7)
= 5/9 + 4/9 . 1
= 5/9 + 4/9
= 1
= - 5/9 + 8/15 + -2/11 + -4/9 + 7/15
= ( -5/9 + -4/9 ) + (8/15 + 7/15 ) + -2/11
= ( -1 ) + 1 + ( -2/11 )
= -2/11
- k nhe năn nỉ ó !!!!!
a,-5/9 + 8/18 + -2/11 + 4/-9 + 7/15 b,5/17 + -9/15 + -2/17 + 2/5 + 14/17
= -5/9 + 4/9 + -2/+ 4/-9 + 7/15 = 5/17 + -3/5 + -2/17 + 2/5 + 14/17
=(-5/9 + 4/9 + -4/9 ) +-2/11 + 7/15 = ( 5/17 + -2/17 + 14/17) + ( 2/5 + -3/5)
= -1/3 + -2/11 + 7/15 =1 + -1/5
=-75/225 + -30/ 225 + 77/225 =4/5
= -25/225 = -1/9 ( 4/5 = 0.8 )
B=-5/9+8/15+-2/11+4/9+7/15
=>B=(-5/9+4/-9)+(8/15+7/15)-2/11
=>B=(-5/9+-4/9)+1-2/11
=>B=-1+1-2/11
=>B=-2/11
Vậy B=-2/11
Ta có :
B=-5/9+8/15+-2/11+4/9+7/15
=>B=(-5/9+4/-9)+(8/15+7/15)-2/11
=>B=(-5/9+-4/9)+1-2/11
=>B=-1+1-2/11
=>B=-2/11
Vậy B=-2/11
\(\dfrac{-5}{9}+\dfrac{8}{15}+\dfrac{-2}{11}+\dfrac{4}{-9}+\dfrac{7}{15}\)
=\(\left(\dfrac{-5}{9}+\dfrac{-4}{9}\right)+\left(\dfrac{8}{15}+\dfrac{7}{15}\right)-\dfrac{2}{11}\)
=\(-1+1-\dfrac{2}{11}=\dfrac{-2}{11}\)
\(=\left(\dfrac{-5}{9}+\dfrac{-4}{9}\right)+\left(\dfrac{8}{15}+\dfrac{7}{15}\right)+\dfrac{-2}{11}\\ =-1+1+\dfrac{-2}{11}\\ =0+\dfrac{-2}{11}=\dfrac{-2}{11}\)