Tính tổng A
A= ( $\frac{3}{1.8}$ +$\frac{3}{8.15}$ +$\frac{15}{22}$ +….$\frac{3}{106.113}$) – ( $\frac{25}{50.55}$+ $\frac{25}{55.60}$+….+ $\frac{95}{100}$ )
Mong các bạn giúp ạ ! Hứa vote :33
Tính tổng A A= ( $\frac{3}{1.8}$ +$\frac{3}{8.15}$ +$\frac{15}{22}$ +….$\frac{3}{106.113}$) – ( $\frac{25}{50.55}$+ $\frac{25}{55.60}$+….+ $\fr
By Raelynn
Đáp án:
`A=847/2260`
Giải thích các bước giải:
đề sai 1 số chỗ nên mk đã sửa lại :
`A=(3/1.8+3/8.15+3/15.22+…+3/106.113)-(25/50.55+25/55.60+…+25/95.100)`
đặt `B=3/1.8+3/8.15+3/15.22+…+3/106.113`
`=3/7 . (1-1/8+1/8-1/15+1/15-1/22+…+1/106-1/113)`
`=3/7 . (1-1/113)`
`=3/7 . 112/113`
`=48/113`
đặt `C=25/50.55+25/55.60+…+25/95.100`
`=5 . (1/50-1/55+1/55-1/60+…+1/95-1/100)`
`=5 . (1/50-1/100)`
`=5 . 1/100`
`=1/20`
từ đó ta có :
`A=B-C` hay `A=48/113-1/20`
`=>` `A=847/2260`
Đáp án:
`A=847/2260`
Giải thích các bước giải:
`A=(3/1.8+3/8.15+15/22+…3/106.113)-(25/50.55+25/55.60+…+95/100)`
SỬA ĐỀ:
`A=(3/1.8+3/8.15+3/15.22+…+3/106.113)-(25/50.55+25/55.60+…+25/95.100)`
`A=[3/7(7/1.8+7/8.15+7/15.22+…+7/106.113)]-[5(5/50.55+5/55.60+…+5/95.100)]`
`A=[3/7(1-1/8+1/8-1/15+1/15-1/22+…+1/106-1/113)]-[5(1/50-1/55+1/55-1/60+…+1/95-1/100)]`
`A=[3/7(1-1/113)]-[5(1/50-1/100)]`
`A=[3/7(113/113-1/113)]-[5(2/100-1/100)]`
`A=[3/7. 112/113]-[5. 1/100]`
`A=48/113-1/20`
`A=960/2260-113/2260`
`A=847/2260`
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