The sum of an infinite geometric series is 450, while the common ratio of the series is 4/ 5 . what is the first term of the series? a) 22 1 2 b) 45 c) 90 d) 180

answer is 90 for first term

Step-by-step explanation:

Let the terms be  

First term x

We will use the formula s∞=x/1−r to find the sum of an infinite geometric series, where −1<r<1.  

We know the sum and the common ratio, so we'll be solving for x where r =4/5

s∞=x/1−r

450=x/1−4/5

450=x/1/5

450=5x

x=90

this is the first term x1 = 90

we know that common ratio is 4/5, so multiplying the first term by factor 4/5 to get the second term  

90 x 4/5=   72 second term  

C) 90

Step-by-step explanation:

The sum of an infinite geometric series is:

S = a₁ / (1 − r)

where a₁ is the first term and r is the common ratio.

450 = a₁ / (1 − 4/5)

450 = a₁ / (1/5)

450 = 5a₁

a₁ = 90