Toán A= (1+1phần 1.3 )+(1+1phần 2.4)+(1+1phần 3.5)…(1+1phần 2018.2020) 03/09/2021 By Eloise A= (1+1phần 1.3 )+(1+1phần 2.4)+(1+1phần 3.5)…(1+1phần 2018.2020)
Đáp án: A = 2018 + ( 2016/2017 + 1009/2020) :2 Giải thích các bước giải: A= ( 1+ 1/1.3)+ ( 1+ 1/2.4)+….+ (1+ 1/2018. 2020) A= (1+ 1+ 1+ 1+…+1) + ( 1/1.3+ 1/2.4+ 1/3.5 + ….+ 1/2028.2020) Đặt 1/1.3+ 1/2.4+ 1/3.5 + ….+ 1/2028.2020 = B Ta có: B = 1/1.3+ 1/2.4+ 1/3.5 + ….+ 1/2018.2020 B= ( 1/1.3+ 1/3.5 +…+ 1/2017. 2019) + ( 1/2.4+ 1/4.6+…+ 1/2018.2020) 2. B = 2. ( 1/1.3+ 1/3.5+…+ 1/2017. 2019) + 2. ( 1/2.4+ 1/4.6+…+ 1/2018.2020) 2.B = ( 2/1.3+ 2/3.5+….+ 2/2017. 2019) + ( 2/2.4 + 2/4.6+…+ 2/2018.2020) 2.B = ( 1- 1/3+ 1/3- 1/5+…..+ 1/2017-1/2019) + ( 1/2 – 1/4+ 1/4 – … + 1/2018 – 1/2020) 2.B = ( 1- 1/2017) + ( 1/2- 1/2020) 2.B = 2016/2017 + 1009/2020 B = ( 2016/2017 + 1009/2020) : 2 ⇒ A = 2018 + ( 2016/2017 + 1009/2020) :2 Nhớ kiểm tra lại nhé, học tốt! Trả lời
Đáp án:
A = 2018 + ( 2016/2017 + 1009/2020) :2
Giải thích các bước giải:
A= ( 1+ 1/1.3)+ ( 1+ 1/2.4)+….+ (1+ 1/2018. 2020)
A= (1+ 1+ 1+ 1+…+1) + ( 1/1.3+ 1/2.4+ 1/3.5 + ….+ 1/2028.2020)
Đặt 1/1.3+ 1/2.4+ 1/3.5 + ….+ 1/2028.2020 = B
Ta có:
B = 1/1.3+ 1/2.4+ 1/3.5 + ….+ 1/2018.2020
B= ( 1/1.3+ 1/3.5 +…+ 1/2017. 2019) + ( 1/2.4+ 1/4.6+…+ 1/2018.2020)
2. B = 2. ( 1/1.3+ 1/3.5+…+ 1/2017. 2019) + 2. ( 1/2.4+ 1/4.6+…+ 1/2018.2020)
2.B = ( 2/1.3+ 2/3.5+….+ 2/2017. 2019) + ( 2/2.4 + 2/4.6+…+ 2/2018.2020)
2.B = ( 1- 1/3+ 1/3- 1/5+…..+ 1/2017-1/2019) + ( 1/2 – 1/4+ 1/4 – … + 1/2018 – 1/2020)
2.B = ( 1- 1/2017) + ( 1/2- 1/2020)
2.B = 2016/2017 + 1009/2020
B = ( 2016/2017 + 1009/2020) : 2
⇒ A = 2018 + ( 2016/2017 + 1009/2020) :2
Nhớ kiểm tra lại nhé, học tốt!