Question

plz answer this as its urgent
ques 42

Answer 1

Answer: the question is asked for 3 or 4marks first of all.

Step-by-step explanation:

Given sum of first n terms is 5n^2+3n.

And mth term is 168

To find

1)value of m

2)then 20th terms

Taking n as 1

S1=5(1)^2+3(1)

S1=5(1)+3(1)

S1=8.

Taking n as 2

S2=5(2)^2+3(2)

S2=5(4)+3(2)

S2=20+6

S2=26.

As we know a1=s1

So

s2

a+a+d=26

8+8+d=26

16+d= 26

D =10

So substitute value of d in mth term so

168=a +(m-1)d

168=8+(10m-10)

168=-2+10m

170=10m

M= 17.

So 20th term=

a+19d

8+19(10)

8+190

198

Hence value of m is 17 and 20th term of AP is 198.

Hope so your are satisfied

Mark me as brainliest

Answer 2

✨☺HERE IS YOUR ANSWER ☺✨

GIVEN :
✨Sn = 5n²+3n

◾if we put n =1
so,,
S1 = 5(1)²+ 3(1)

S1 = a(first term) = 8

◾if we put , n=2
so,
S2 = 5(2)²+3(2)
so, S2 = 26

S2 = a1 + a2
(a1 = 8)by above-
so,
26-8 = a2 (2nd term)
a2= 18

now ,, we know that ,
common difference ,D = a2-a1
so, D = 18-8 = 10
given ,
Mth term = 168

a+ (m-1) d = 168
8+(m-1)10 = 168
m = 17th term ans.
so, ◾mth term is 17th term ans.

now , 20th term = a+19d

= 8+19(10)
= 198 answer

✨☺hope it helps you ☺✨