(a+b+c+d)^2-(a-b+c-d)^2怎么算
2(a b)-c.d怎么算
(a+b+c+d)^2-(a-b+c-d)^2怎么算
a,b,c,d>0 求证:a/(b+c)+b/(c+d)+c/(d+a)+d/(a+b)大于等于2,怎么证明,
a>b>c>d>0.a/b=c/d怎么证明a+d>c+b
(A-B)(C-D) 怎么算
(a-b)(c-d)怎么算?
a,b,c,d>0 证(a/(b+2c+3d))+(b/(c+2d+3a))+(c/d+2a+3b))+(d/(a+2b
[a,b)×[c,d
a,b ,c ,d
已知a/b=c/d,求证a+2b/b=c+2d/d
求行列式 |a+b+c+2d a b c,d b+c+d+2a b c,d a a+c+d+2b c,d a b a+b
A B C D × 9 ___________________ D C B A (1) A = ( )(2) B = (