A=1/2 + 5/6 + 11/12 + 19/20 + 29/30 + 41/42 + 55/56 + 71/72 + 89/90 19/09/2021 Bởi Ayla A=1/2 + 5/6 + 11/12 + 19/20 + 29/30 + 41/42 + 55/56 + 71/72 + 89/90
A=1/2 + 5/6 + 11/12 + 19/20 + 29/30 + 41/42 + 55/56 + 71/72 + 89/90 = 1 – 1/2 + 1 – 1/6 + 1-1/12 + 1 – 1/20 + 1 – 1/30 + 1 – 1/42 + 1 – 1/56 + 1/72 + 1 – 1/90 = ( 1 + 1 + 1 + 1 + 1 +1 + 1 + 1 +1 ) – ( 1/2 + 1/6 + 1/12 + 1/20 + 1/20 + 1/30 + 1/42 + 1/56 + 1/72 + 1/90 ) = 9 – ( 1 / 1.2 + 1 / 2.3 + … 1/9.10 ) = 9 – ( 1 – 1/2 + 1/2 – 1/3 + 1/3 – 1/4 + … + 1/9 – 1/10 ) = 9 – ( 1 – 1/10 ) = 9 – 9/10 = 81/10 Bình luận
Đáp án:
Giải thích các bước giải:
Chúc bạn học tốt
A=1/2 + 5/6 + 11/12 + 19/20 + 29/30 + 41/42 + 55/56 + 71/72 + 89/90
= 1 – 1/2 + 1 – 1/6 + 1-1/12 + 1 – 1/20 + 1 – 1/30 + 1 – 1/42 + 1 – 1/56 + 1/72 + 1 – 1/90
= ( 1 + 1 + 1 + 1 + 1 +1 + 1 + 1 +1 ) – ( 1/2 + 1/6 + 1/12 + 1/20 + 1/20 + 1/30 + 1/42 + 1/56 + 1/72 + 1/90 )
= 9 – ( 1 / 1.2 + 1 / 2.3 + … 1/9.10 )
= 9 – ( 1 – 1/2 + 1/2 – 1/3 + 1/3 – 1/4 + … + 1/9 – 1/10 )
= 9 – ( 1 – 1/10 )
= 9 – 9/10
= 81/10