` a=8,a_n =62 ` और `S_n =210 ` दिया है| n और d ज्ञात कीजिए| एक `A.P. ` में ,

Explanation

`` " " a=8 , a_n =62 `
`" " S_n =210`
` rArr " " (n)/(2) (a_+a_n) =210`
` rArr " " (n)/(2) (8+62)=210`
` rArr " " n = (210xx2)/(70 ) =6`
तथा ` " " a_n =62 rArr " " a+ (n-1) d=62`
` rArr " " 8+ (6-1) d=62 " " rArr " " 5d =62 -8 =54`
` rArr " " d =(54)/(5)`
`therefore " " n= 6,d =(54)//(5)`