8A = 1.3.5.8 + 3.5.7.8 + 5.7.9.8 + … + 95.97.99. = 1.3.5(7 + 1) + 3.5.7(9 - 1) + 5.7.9(11 - 3) +… +95.97.99(101 - 93) = 1.3.5.7 + 15 + 3.5.7.9 - 1.3.5.7 + 5.7.9.11 - 3.5.7.9 + …+ 95.97.99.101 - 93.95.97.99 = 15 + 95.97.99.101 8A={15+95.97.99.101}/{8} = 11 517 61313 ko bt có đúng ko,chúc bn học tốt

mk ko viết đề nhé

C=1.3.5.8 + 3.5.7.8 + 5.7.9.8 + … + 95.97.99.8

C= 1.3.5(7 + 1) + 3.5.7(9 - 1) + 5.7.9(11 - 3) + … + 95.97.99(101 - 93)

C= 1.3.5.7 + 15 + 3.5.7.9 - 1.3.5.7 + 5.7.9.11 - 3.5.7.9 + … + 95.97.99.101 - 93.95.97.99

C= 15 + 95.97.99.101

=>C=\frac{15 + 95.97.99.101}{8}

1.3.5.8 + 3.5.7.8 + 5.7.9.8 + … + 95.97.99.8

= 1.3.5(7 + 1) + 3.5.7(9 - 1) + 5.7.9(11 - 3) + … + 95.97.99(101 - 93)

= 1.3.5.7 + 15 + 3.5.7.9 - 1.3.5.7 + 5.7.9.11 - 3.5.7.9 + … + 95.97.99.101 - 93.95.97.99

=15 + 95.97.99.101

=> A = \frac{15.95 + 97.99.101}{8}

1.3.5+3.5.7+5.7.9+...+97.99.101

=(101-2).(101-1).101.(101+1):4

=25497450

1.3.5.8 + 3.5.7.8 + 5.7.9.8 + … + 95.97.99.8

= 1.3.5(7 + 1) + 3.5.7(9 - 1) + 5.7.9(11 - 3) + … + 95.97.99(101 - 93)

= 1.3.5.7 + 15 + 3.5.7.9 - 1.3.5.7 + 5.7.9.11 - 3.5.7.9 + … + 95.97.99.101 - 93.95.97.99

= 15 + 95.97.99.101

=> \(A=\frac{15.95+97.99.101}{8}\)

Tách ra rồi tính

Bài này rất dễ may cho bạn là hôm nay minh rảnh nên mới giải cho tiết.Thôi tớ làm nhé!

Theo bài ra ta có :

A =1.3.5+3.5.7+5.7.9+...+97.99.101

8A=8.(1.3.5+3.5.7+5.7.9+...+97.99.101)

8A=1.3.5.8+3.5.7.8+5.7.9.8+...+97.99.101.8

8A=1.3.5.(7+1)+3.5.7(9-1)+5.7.9.(11-3)+...+97.99.101.(103-95)

8A=1.3.5.7+1.1.3.5+3.5.7.9-1.3.5.7+5.7.9.11-3.5.7.9+...+97.99.101.103-95.97.99.101

8A=1.1.3.5+97.99.101.103

8A=15+99900009

8A=99900024

A =99900024:8

A =12487503

Vậy A=12487503