(62 + 72 + 82 + 92 + 102) - (12 + 22 + 32 + 42 + 52)
= (62 - 12) + (72 - 22) + (82 - 32) + (92 - 42) + (102 - 52)
= (6 - 1).(6 + 1) + (7 - 2).(7 + 2) + (8 - 3).(8 + 3) + (9 - 4).(9 + 4) + (10 - 5).(10 + 5)
= 5.7 + 5.9 + 5.11 + 5.13 + 5.15
= 5.(7 + 9 + 11 + 13 + 15)
= 5.55
= 275