Sir\Madam please explain me this question on Arithmetic Progressions!!

Let the four parts be a-3d, a-d, a+d and a+3d.

a-3d + a-d + a+d + a+3d = 20

a = 5.

(a-3d)(a+3d)/((a-d)(a+d)) = 2/3

(a²-9d²)/(a²-d²) = 2/3

(25-9d²)/(25-d²) = 2/3

(25-9d²)= (2/3)(25-d²)

25 - 9d²= 50/3 - 2d²/3

This gives d = ±1,

Hence the four parts are,

2, 4, 6, 8

Regards,

Team,

TopperLearning.