a1+a2+……an=40*5=200
(a1-5)^2+(a2-5)^2+……+(an-5)^2=3*40=120
=a1^2+a2^2+……+an^2-10(a1+a2+……+an)+25*40
=a1^2+a2^2+……+an^2-1000
所以
a1^2+a2^2+……+an^2=1120