Question

The 4th term of a G.P. is square of its second term, and the first term is – 3. Determine its 7th term.

Answer 1

Given: a4 = (a2)2 and a = –3

We know that in G.P an = arn-1

∴ a2 = (–3) × r2-1 = –3r(∵ a = –3)

Similarly,

a4 = –3r3

∴ –3r3 = (-3r)2 (∵ a4 = (a2)2 )

∴ –3r3 = 9r2

⇒ r = –3

∴ r = –3

Now,

a7 = ar7-1

⇒ a7 = (–3)( –3)6 (∵ a = –3 and r = –3)

⇒ a7 = ( –3)7 = – 2187.

∴ a7 = – 2187

JAI SHREE KRISHNA

Answer 2

The same thing you have hidden