Q no 7 and 8 solve both

Asked by sucharitasahoo1 | 26th Nov, 2017, 10:09: AM

Expert Answer:

begin mathsize 16px style straight S subscript straight n equals end subscript straight n over 2 left parenthesis 2 straight a plus left parenthesis straight n minus 1 right parenthesis straight d right parenthesis
straight n over 2 left parenthesis 2 straight a plus left parenthesis straight n minus 1 right parenthesis straight d right parenthesis equals 1 half left parenthesis 5 straight n squared plus 3 straight n right parenthesis
2 straight a plus left parenthesis straight n minus 1 right parenthesis straight d equals left parenthesis 5 straight n plus 3 right parenthesis
2 straight a minus straight d plus nd equals 5 straight n plus 3
comparing
straight d equals 5
2 straight a minus straight d equals 3...... straight a equals 4
sub
straight t subscript 40 equals straight a plus 39 straight d end style

Answered by Arun | 26th Nov, 2017, 05:12: PM