Question

if the sum of n term of the ap is 3x^2 +5x and its mth term is 164 then the value of m is​

Answer 1

Answer:

Let S

n

denote the sum of n terms and a

n

be the nth term of the given AP. Then,

S

n

=3n

2

+5n

S

n−1

=3(n−1)

2

+5(n−1)=3n

2

−n−2

Now, a

n

=S

n

−S

n−1

a

n

=(3n

2

+5n)−(3n

2

−n−2)

a

n

=6n+2

Now, a

m

=164

6m+2=164

6m=162

m=27