Question

Find the 11th term of this sequence -10, 20, -40

Answer 1

-10,240.

Explanation:

This is a geometric sequence with common ratio 20/-10 = -40/20 = -2.

The nth term = a1r^(n-1) where a1 = the first term and r = the common ratio, so the 11th term = -10 * (-2)^ (11-1)

= -10 * 1024

= -10,240.

Answer 2

Explanation:

the nth term of the geometric sequence is : An =A1 × r^(n-1)

A1 = -10

r= -40/20=20/-10=-2

n =11

A11 = -10× (-2)^(11-1)

A11 = -10× (-2)^(10)

A11 = - 10240