Question

1- find the first term= ?, 90, 540, 3240

Answer 1

Answer:

1. 15

2. 8

Step-by-step explanation:

The two sequence are geometric progression GP, because they follow a constant multiple (common ratio)

The nth term of a GP is;

Tn = ar^(n-1)

Where;

a = first term

r = common ratio

For the first sequence;

The common ratio r is

r = T3/T2 = 540/90 = 6

r = 6

T2 = ar^(2-1) = ar

T2 = 90 = ar

Substituting the values of r;

90 = a × 6

a = 90/6

a = 15

First term = 15

2. The sam method applies here.

Common ratio r = T3/T2 = 128/32 = 4

r = 4

T2 = ar^(2-1) = ar

T2 = 32 = ar

Substituting the values of r;

32 = a × 4

a = 32/4

a = 8

First term = 8