# (A + B-x) / C + (A + C-x) / b + (C + B-x) / a + (4x) / (A + B + C) = 1 #
# => (A + BX) / C + 1 + (A + cx) / b + 1 + (C + BX) / A + 1 + (4x) / (A + B + C) -3-1 = 0 #
# => (A + B + C-x) / C + (A + C + B-x) / b + (C + B + A-x) / A-4 (1-x / (A + B + C)) = 0 #
# => (A + B + C-x) (1 / C + 1 / B + 1 / ก) -4 ((A + B + C-x) / (A + B + C)) = 0 #
# => (A + B + C-x) (1 / C + 1 / B + 1 / A-4 / (A + B + C)) = 0 #
ดังนั้น
# => (A + B + C-x) = 0 #
สำหรับ # (1 / C + 1 / B + 1 / A-4 / (A + B + C))! = 0 #
ด้วยเหตุนี้ # x = A + B + C #
