If a geometric sequence has u5 = 40 and u10 = 303.75, find the value of u15

Step-by-step explanation:

The  nth term of a geometric sequence is expressed as Un = ar^n-1

a is the first term

r is the common ratio

n is the number of terms

U5 = ar^5-1 = 40

ar^4 = 40 1

Also U10 = ar^9 = 303.75 2

Divide equation 2 by 1

ar^9/ar^4 = 303.75/40

r^5 = 7.59375

r = 1.5

substitute r = 1.5 into equation 1

ar^4 = 40

a(1.5)^4 = 40

a(5.0625) = 40

a = 40/5.0625

a = 7.9

u15 = ar^14

u15 = 7.9(1.5)^14

u15 = 291.93 * 7.9

u15 = 2306.24

the 3rd on is correct

step-by-step explanation: