Question no. 4 please
Attachments:
Answers
Answered by
1
AP:9,17,25,........
here a=9,d=a2-a1=8
Sn=636
n/2(2a+(n-1)d)=636
n/2(2(9)+(n-1)(8))=636
n/2(18+8n-8)=636
n/2(10+8n)=636
10n+8n^2=1272
8n^2+10n-1272=0
4n^2+5n-636=0
n^2+(5/4)n- (636/4)=0
n^2+(5/4)n-159=0
n^2+2(5/8)(n)+(5/8)²-(5/8)²-159=0
(n+(5/8))²-(25/64)-159=0
(n+(5/8))²-(10201/64)=0
n+(5/8)=√(10201/64)
n+(5/8)=+or- 101/8
n=(101/8)-(5/8) n=(-101/8)-(5/8)
n=96/8. n=-106/8
n=12. n=-53/4
here a=9,d=a2-a1=8
Sn=636
n/2(2a+(n-1)d)=636
n/2(2(9)+(n-1)(8))=636
n/2(18+8n-8)=636
n/2(10+8n)=636
10n+8n^2=1272
8n^2+10n-1272=0
4n^2+5n-636=0
n^2+(5/4)n- (636/4)=0
n^2+(5/4)n-159=0
n^2+2(5/8)(n)+(5/8)²-(5/8)²-159=0
(n+(5/8))²-(25/64)-159=0
(n+(5/8))²-(10201/64)=0
n+(5/8)=√(10201/64)
n+(5/8)=+or- 101/8
n=(101/8)-(5/8) n=(-101/8)-(5/8)
n=96/8. n=-106/8
n=12. n=-53/4
Similar questions