Given d=9,S10=915 Find a and a10
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Answered by
4
Answer:
d=9
S10=915
a= ?
S10=10/2{2.a+(10-1).9}=915
=> 5(2a+9.9)=915
=> 2a+81=915/5=183
=> 2a=183-81
=> 2a=102
=> a=51
a10=a+(n-1).d
=51+(10-1).9
=51+9.9
=51+81
=132
Answered by
3
Answer:
Sn= n/2 (2a+(n-1)d)
S10= 5 (2a+9×9)=915 => 10a+405=915
=> 10a= 915-405
=> a = 510/10
=> a = 51
a10 = a+(n-1)d
a10= 51 + 9×9
a10 = 51 + 81
a10 = 132
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