Cho a/b = c/d. Chứng minh (a - b)^2/(c - d)^2 = 3a^2 + 2b^2/3c^2 + 2d^2

cho a/b = c/d. Chứng minh :
a) ( a - b)^2/( c-d )^2 = 3a^2 +2b^2/3c^2+ 2d^2
b) ( a - b/c-d)^2005 = 2a^2005 - b^2005/2c^2005 - d^2005