( 998 ) 2
计算:(2+5)(2﹣5)﹣(﹣)2.
(1)计算:+(π-3)0-tan45°;(2)计算:()÷.
已知,如图,点B、E、C、F四点在同一条直线上,AB∥DE,AB=DE,AC、DE相交于点O,BE=CF.求证:AC=DF.
计算:[(x+2y)2﹣(x+2y)(x﹣2y)]÷8y.
计算:.