B,根據(jù)比例的性質(zhì)可知該等式不成立,錯誤.
C,根據(jù)乘法交換律,交換兩內(nèi)項的位置,應(yīng)是
a |
c |
b |
d |
D,若
a |
b |
c |
d |
a?b |
b |
c?d |
d |
a+b |
b |
c+d |
d |
①÷②,得
a?b |
a+b |
c?d |
c+d |
故選D.
a |
b |
c |
d |
a+m |
b+m |
c+m |
d+m |
a+m |
b |
c+m |
c |
a |
c |
d |
b |
a?b |
a+b |
c?d |
c+d |
a |
c |
b |
d |
a |
b |
c |
d |
a?b |
b |
c?d |
d |
a+b |
b |
c+d |
d |
a?b |
a+b |
c?d |
c+d |