化简:(2x﹣5)2﹣(2x+5)2.
解:原式=(2x﹣5+2x+5)(2x﹣5﹣2x﹣5)
=4x(﹣10)
=﹣40x.
A good solution to the problem _________at the meeting.
A.came about
B.came along
C.came up
D.came to
试结合矿物的标本,阐述矿物主要的物理性质特征如颜色、光泽、解理、断口、结晶形态和硬度等的基本概念。