Question

What is n^th term of a G.P.?

(a) an = a + (n-1) d

(b) an = a + (n) d

(c) an = a*r^n-1

(d) an = a*r^n

The question was asked by my school principal while I was bunking the class.

Question is taken from Geometric Progression(G.P.) in portion Sequences and Series of Mathematics – Class 11

Answer 1

Right option is (c) an = a*r^n-1

To explain: Since every term of an G.P. is r times the previous term.

i.e. an+1 = an * r = an-1 * r^2 = ….. = a1 * r^n

or an = a*r^n-1