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a) 7/15+14/15+13/15=(7/15+13/15)+14/15=20/15+14/15=34/15
b)13/4+4/9+7/8=(13/4+7/8)+4/9=(26/8+7/8)+4/9=33/8+4/9=297/72+32/72=329/72
a. 7/15 + 14/15 + 13/15
= 7+14+13/ 15
= 34/15
b.13/4 + 4/9 + 7/8
= [ 13/4 + 7/8 ] + 4/9
= [ 26/8 + 7/8 ] + 4/9
= 33/8 + 4/9
= 297/72 + 32/72
= 329/72
`4/6+7/13+17/9+19/13+1/9+14/6`
`=(4/6+14/6)+(7/13+19/13)+(17/9+1/9)`
`=18/6+26/13+18/9`
`=3+2+2`
`=7`
1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20
=(1+19)+(2+18)+(3+17)+(4+16)+(5+15)+(6+14)+(7+13)+(8+12)+(9+11)+20+10
=20+20+20+20+20+20+20+20+20+20+10
=20×10+10
=200+10
=210
= ( 1 + 19 ) + ( 2 + 18 ) + ( 3 + 17 ) + (4 + 16 ) + ( 5 + 15 ) + ( 6 + 14 ) + ( 7 + 13 ) + ( 8 + 12) + ( 9+ 11 ) + 20
= 20 + 20 + 20 +20 + 20 +20 + 20 + 20 + 20 +20
= 20 x 10
= 200
tui đầu tiên đó
Giúpppp mìnhh vớiiiiiiiiiiiiiiiiiiiiiiiii nhanhhhhhhhhhhh lênnnnnnnnnnnnnnnnn
\(\dfrac{8}{7}+\dfrac{13}{14}\)
\(=\dfrac{16}{14}+\dfrac{13}{14}\)
\(=\dfrac{29}{14}\)
\(\dfrac{8}{7}+\dfrac{13}{14}=\dfrac{16}{14}+\dfrac{13}{14}=\dfrac{29}{14}\)