Math, asked by adityathombre1440, 5 months ago


For a G.P.
i)
If t3 = 20, t6= 160, find S7.
ii) If t4 =16, t9=512, find S10.​

Answers

Answered by Anonymous
3

Answer:

Step-by-step explanation:

Let a and r and first term nad common ratio

Then t3=ar²=20

t6=ar^5=160

t6/t3=ar^5/ar^2=160/20

=r³=8

r=2

ar^2=20

a*4=20,a=5

So S7=a(r^7-1)/(r-1)

=5(2^7-1)/(2-1)

=5*(128-10=127*5=635

========================

ii) If t4 =16, t9=512, find S10.​

t9/t4=ar^8/ar^3=r^5=512/16=32=25

r=2

r4=ar^3=16

a*8=16

a=2

s1o=a(r^10-1)/(r-1)

=2(2^10-1)/(2-1)

=2(1024-1)

=2*1023=2046

Similar questions