填空并加以证明. 已知x>0,y>0,若将3xy:(x﹣y)中的x、y扩大2倍,则3xy:(x﹣y)的值就 .
42×56+56×56=56×(42+56)应用了乘法结合律 .(判断对错)
根据运算定律填空. (1)12.5×3.4×0.8=( × )× (2)4.36×2.5+ ×2.5=( +5.64)× (3)6.5×2.4+6.5×7.6= ( ) (4)(6+0.6)×0.25= + .
a×m+b×m=(□+□)○m (580+470)÷70=580○□○□○□ 625÷(□○2)=□×2○50.
53×26+53×74=53×(26+74)应用了 .
数学医院. 36×99 =36×(100﹣1) =3600﹣1 =3599 125×4×8×25 =(125×8)+(4×25) =1000+100 =1100