C-11-Q086mediumsingle_mcqThe proof of (a+bb+c)2=a2+b2b2+c2\left(\dfrac{a+b}{b+c}\right)^2 = \dfrac{a^2+b^2}{b^2+c^2}(b+ca+b)2=b2+c2a2+b2 given a:b=b:ca:b = b:ca:b=b:c uses the substitution b2=acb^2 = acb2=ac and the expansion—a(a+b)2=a2+2ab+b2(a+b)^2 = a^2 + 2ab + b^2(a+b)2=a2+2ab+