a+b=5
(10a+c)(10b+c)
=100ab+10(a+b)c+c^2
=100ab+10*5c+c^2
=50(2ab+c)+c^2
题有误
较小正方形的面积比原正方形的面积减少了
a^2-(a-b)^2
=(a+a-b)(a-a+b)
=b(2a-b)
a+b=5
(10a+c)(10b+c)
=100ab+10(a+b)c+c^2
=100ab+10*5c+c^2
=50(2ab+c)+c^2
题有误
较小正方形的面积比原正方形的面积减少了
a^2-(a-b)^2
=(a+a-b)(a-a+b)
=b(2a-b)