Question

किसी समांतर श्रेणी का 3 पद 18 पद 30 श्रेणी के 17 पदों का योग ज्ञात करो

Answer 1

Hay dear friend according to the question we know that

T3 = 18
T7 = 30

so,

we also write it this form

a + 2d =18 -----------(1)
a + 6d = 30 ----------(2)

if we subtract both equations then we get
d = 4 Now,

if we put the value of d in the first equations so

a + 2×4 = 18

a + 8 = 18

a = 18-8

a = 10

Then,

we know that formula - Sn = n/2(2a +(n-1)d)

Sn = 17/2(2×10(17-1)4)

Sn = 17/2(20+64)

Sn = 17/2×84

Sn = 714

I hope it's help you