x2+49+______=(x+7)2.
(x+7)2=x2+49+14x,
故x2+49+14x=(x+7)2.
_______ seems strange to us is ______ the troublesome boy is getting along well with all his teachers. [ ]
A. It; that
B. What; how
C. It; how
D. What; that
高干桑到一定树龄后,花果较少,叶形大,秋叶硬化晚。