(a + b)prop_to(c) & (b+c)prop_to(a). prove that (a+c)prop_to(b).

Answer 1

(a+b)/c = (b+c)/a

a(a+b) = c(b+c)

a^2 + ab = bc + c^2

a^2 - c^2 = bc - ab

(a+c)(a-c) = b(c-a)

(a+c) = (-1)b

(a+c)/b = -1

end of proof