Question

4. Find four numbers is GP. such that the product of the extremes is 72 and the sum of the middle twois 18.​

Answer 1

Answer:

AP:9,10.5,12,13.5.........

Step-by-step explanation:

four numbers in an AP are in the form of:-

a-2d , a-d , a+d , a+2d

ATQ

(a-2d)(a+2d)=72

a²+2da-2da-4d²=72

a²-4d²=72.............(1)

a-d+a+d=18

2a=18

a=9

putting the value of a in eqn (1)

9²-4d²=72

81-4d²=72

9=4d²

9/4=d²

3/2=d

AP:9,10.5,12,13.5.........