Chứng minh rằng

cho cac so a,b,c,d thoa manb^2=ac;c^2=bd(voia,b,c,d khac o;2b+3c khac 5d ;b^3+c^3 khac d^3)

chung minh rang: a^3+b^3-c^3/b^3+c^3-d^3=(2a+3b-5c/2b+3c-5d)^3