let four numbers in a.p. be:
a-3d,a-d,a+d,a+3d
their sum=(a-3d)+(a-d)+
(a+d)+(a+3d)=20
=> 4a=20 =>a=5
also sum of squares=120
i.e. (a-3d)2+(a-d)2
+(a+d)2+(a+3d)2=120
{where 2 means square }
=>a2-6ad+9d2-2ad +d2+
a2+2ad+d2+a2+6ad+9d2=120
=>4a2=20d2=120
=>4(25)=20d2=120
=>20d2+20 =>d2=1
=>d=+_1
hence the numbers are
5-3,5-1,5-1,5-3
or 5-3,5-1,5-1,5-3
i.e. 2,4,6,8 or8,6,4,2
