Question

if Sn=6n+7n2 then find 15th term of ap​

Answer 1

Answer:

s15= 6(15)+7(15)^2

= 90+1575

= 1665

Answer 2

Answer:

Step-by-step explanation:

Sn=6n+7n+2

substitute n as 1

S1 = 6+7+2 = 15

there fore  first term that is a=15

now substitute n=2

S2=12+14+2

S2 is nothing but a+a2

therefore

a+a2=28

a2=28-15=13

d=a2-a1=2

a15=a+(n-1)d

     = 15+(15-1)2

     = 15+28

    = 43

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