Question

If the sum of the first n terms of Ap is 3n-2n , find the 18 term of the AP

Answer 1

Step-by-step explanation:

$\sf \blue{ s_{n} = 3n - 2 n } \\ \sf \red{ a_{18} =? } \\ \sf \green{s_{1} = 3 \times 1- 2 \times 1} \\ \sf \green{s_{1} = 3 - 2} \\ \sf \green{s_{1} = 1 = a} \\ \sf \green{s_{2} = 3 \times 2 - 2 \times 2} \\ \sf \green{s_{2} = 6 - 4} \\ \sf \green{s_{2} = 2} \\ \sf{so..s_{2} = a + a_{2} } \\ \sf{2 = 1 +a_{2} } \\ \sf{a_{2} = 1} \\ \sf{d =a_{2} - a } \\ \sf{d = 1 - 1 = 0} \\ so.... a_{18} = a + 17d \\ \sf{a_{18} = 1 + 17(0)} \\ \sf \orange{ \boxed{a_{18} = 1}}$

Hope my answer will help you...

Answer 2

Answer:

If sum is 3n-2n then simplify it and u will get that the sum is n

So for the 18th term sum is 18.

s18 is 18 so S2=2

so S2= 2/2(a+d)

2=a+d

a= 2-d

s18=18/2(2a+17d)

18=9(2{2-d}+17d)

18/9=4-2d+17d

-2=15d

d=-2/15

substitute value of d in a

a=2-(-2/15)

a=2+2/15

a=(32/15)

then 18th term is a+17d just find the value by substituting the value of a and d

Sorry I didn't have time to find the term. But do mark me as ur brainliest