## a) 2/3: (1/2-3x) = -5/6 b) 1/1.2+ 1/2.3+ 1/3.4+ 1/4.5+…+1/99.100 c)1/1.6+ 1/6.11+ 1/11.16+ 1/16.21+…+1/496.501 d) 8/1.5+ 8/5.9+ 8/9.13+…+ 8/41.4

Question

a) 2/3: (1/2-3x) = -5/6
b) 1/1.2+ 1/2.3+ 1/3.4+ 1/4.5+…+1/99.100
c)1/1.6+ 1/6.11+ 1/11.16+ 1/16.21+…+1/496.501
d) 8/1.5+ 8/5.9+ 8/9.13+…+ 8/41.45
e) S= 1/30+ 1/42+ 1/56+ 1/72+ 1/90+ 1/132
????LÀM GIÚP MÌNH ĐI CÁC CAO NHÂN ????

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4 tuần 2021-08-13T13:17:50+00:00 2 Answers 2 views 0

1.

a) 2/3: (1/2-3x) = -5/6

1/2- 3x= 2/3: -5/6

1/2- 3x= -4/5

3x= 1/2- (-4/5)

3x= 13/10

x= 13/10: 3

x= 13/30

BIẾT LÀM MỖI BÀI NÌ:v

2. a) 2/3: (1/2-3x) = -5/6

1/2- 3x= 2/3: -5/6

1/2- 3x= -4/5

3x= 1/2- (-4/5)

3x= 13/10

x= 13/10: 3

x= 13/30

b) 1/1.2+ 1/2.3+ 1/3.4+ 1/4.5+…+1/99.100

= 1- 1/2+ 1/2 – 1/3+ 1/3- 1/4+1/4- 1/5+…+1/99- 1/100

= 1- 1/100

=99/100

c)1/1.6+ 1/6.11+ 1/11.16+ 1/16.21+…+1/496.501

= 1- 1/6+1/6-1/11+…+1/496- 1/501

= 1- 1/501

= 500/501 nhưng do số thứ 100 có dạng 1/496. 501 nên bằng 1/5. 500/501

= 100/501

d) 8/1.5+ 8/5.9+ 8/9.13+…+ 8/41.45

= 8. ( 1/1.5+ 1/5.9+ 1/9.13+…+1/41.45)

= 2. ( 4/1.5+4/5.9+ 4/9.13+…+4/41.45)

= 2. ( 1- 1/5+ 1/5- 1/9+ 1/9- 1/13+…+ 1/41- 1/45)

= 2. ( 1- 1/45)

= 2. 44/45

= 88/45

e) S= 1/30+ 1/42+ 1/56+ 1/72+ 1/90+ 1/132

S= ( 1/5.6+ 1/6.7+ 1/7.8+ 1/8.9+ 1/9.10)+ 1/132

S= ( 1/5- 1/6+ 1/6- 1/7+ 1/7- 1/8+ 1/8- 1/9+ 1/9- 1/10)+ 1/132

S= ( 1/5- 1/10)+ 1/132

S= 1/10+ 1/132

S= 132/1320+ 10/1320

S= 71/660