计算:a^3(b+c-d)+a^2b(c+d-a)-a^2c(d+a+b)
计算(a+b+c-d)(a-b+c-d)
[a,b)×[c,d
a,b ,c ,d
a,b,c,d>0 证(a/(b+2c+3d))+(b/(c+2d+3a))+(c/d+2a+3b))+(d/(a+2b
(a+b+2c-3d)(a+b-2c+3d)用乘法公式计算.
计算(3a+b-2c+d)(3a-b+2c+d)
计算(a+b+c)(c+d+e)
( )-(c-d)=(a-c)-(-b+d)
已知:a/b=c/d,求证:(2a+3b)/(a+b)=(2c+3d)/(c+d)
已知a/b=c/d,求证2a+3b/a+b=2c+3d/c+d
(a/(b+2c+3d))+(b/(c+2d+3a))+(c/d+2a+3b))+(d/(a+2b+3c))>=2/3
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