Question

If the sum of first n terms of an A.p is n(n+10)then find the first term and common differenve

Answer 1

S1=T1=1(1+10)

          =11

S2=2(2+10)

    =24

T2=S2-S1

    =24-11

     =13

D=T2-T1

  =13-11

  =2

a=11 And D=2...............ans

Answer 2

Answer:

a= 11 and d=2

Step-by-step explanation:

sn=n(n+10)

Therefore,  s1= 1(1+10)= 11

and s1=a

so now a=11

S2=2(2+10)=24

s2-s1=a2

24-11=13

therefore, a2=13

d=a2-a1

=13-11=2

Therefore d=2