If a,b,c,d are proportional, prove that a+d=b+c+(a-b)(a-c) a

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Please find the answer to your question below
If a,b,c,d are proportional, To prove
a+d=b+c+((a-b)(a-c)/a)
a(a-b-c+d) = a^2-ab+ad=a^2 - ab - ac +bc = (a-b)(a-c);
a-b-c+d = +(a-b)(a-c)/a
Soa+d=b+c+((a-b)(a-c)/a)