Question

please answer this question

Answer 1

let the four terms be a-3d, a-d, a+d ,a+3d
then,
a-3d+a-d+a+d+a+3d=75
4a=75
a=75/4
a=18.75

now the terms are
18.75 -3d, 18.75-d, 18.75+d, 18.75+3d

(18.75 -3d)×(18.75+3d)=(18.75-d)×(18.75+d)
18.75²-9d²=18.75²-d²
9d²-d²=1
8d²=1
d²=1/8
d=1/2×2^½
d=2^½/4