Question

If sum of nth term is Sn=3n²+4n. Find the 16th term of A.P

Answer 1

let take n as 1 ;











then

S¹ =3+4=7
so; we will get a¹ as 7

now; putting 2 in n will give;
S²=3(2)²+4*2=12+8=20
S²-S¹ =A²=20-7=13
;A²-A¹ = difference
13-7=6=d
now putting In formula; an =a+ (n-1)d
a16=7+(16-1)6=7+90=97
so 16th term will be 97

Answer 2

Answer:

133

Step-by-step explanation:

sn =3n^2+4n

let n=16

3×16^2+4×16

3×256+64

468+64

532

now we get s16=532

sn=n/2(2a+(n-1)d)

putting the values

532=16/2(2a +15d)

532/8=2a+15d

133/2=2a+15d

133/2×2=a+15d

133=a+15d-------------1

as we know

n16=a+15d------------2

comparring eq^n 1 and 2

133=n16