✨ Best Answer ✨
19,23,27…
は初項19,公差4の等差数列なので
一般項は a(n) = 4n+15
a(10) = 40 + 15 = 55
a(20) = 80 + 15 = 95
等差数列の和は 項数×{ a(10)+a(20) }/2 なので
11 × ( 55 + 95 )/2 = 825
Mathematics
Senior High
Solved
21番の問題の解き方の解説をして欲しいです!
TRIAL B
21 等差数列 19, 23 27...... について,第10項から第20項までの和を求め
よ｡
Answers
Answers
Were you able to resolve your confusion?
Users viewing this question
are also looking at these questions 😉
![(2)[1]の式はなぜこうなるのでしょうか？
解説お願いします🙏🏻 - 1](https://d1e9oo257tadp1.cloudfront.net/uploads/qa_question_image/file/1810073/thumb_l_webp_1717B3E3-8A84-49A5-82D1-466207496D96.webp?Expires=1787345936&Signature=GSL3TrM~7nBMDiw2NLP7D4SJypKCM~66pTSZ7RRiCHuBevhIkLY1QfesuJBX-GqfHK~cWPwVTgneZWaj6Cc-qDCkJyvePE7UVH6r-cL2KxyscgtGzzkz-XdC3vPR5s-6BzdcE1rE5Ig~RgBi5k~ZSzxgSuTk7IJuxNq9deWrTwtgzv0U6uLoNkcMDHYVZfh1cMOLXPu9WlxPMXk~mXNytH-NybJIW2gwUMeCpAQ7xkQcxyVTMnQbxHGooychDo7PSfRfIy6he9tRI2VUG1FOIrQgPqe1jrRFlqK9CaKbLHYRlrW4Ph4323SIOEOxFkL47i6w~vEwy-JyB7GcTiSdzg__&Key-Pair-Id=K2W722D70GJS8W&Expires=1787345936&Signature=T7kPuJv5Cvwmv44UtNkOGJmavzqXo8bDCOIxDmq4tfbgV8nGHcEX60pb9IyIbMplPRGzXwKmYKBSS0GVlRLHCVqEspZoTNqB1Y5ciUnuXiSBSWJkisgtqH1~18OEaukqAr-snqdstqcSpP10As1UfcysxZap3KFgpEL4ZDc5YTyn5ItURnA6T8j~iqC3rlrvmZHohSPmQ5Wknf7doksddI6N46eKpIa1pjwlk5I5qvWaJIw0q8ANlaTTHMij4QN9HrQpSNmqAML2Jx9pCOrlzP95lhvxmJlqy66uNApqIiZt98jDRiBW6mJqBT-3DKFoJQR9zzbfcSbiJ~u-GWDYbQ__&Key-Pair-Id=K2W722D70GJS8W)
公式ありがとうございます
助かります