题目

化简求值：x2-2(x2-3xy) +3 (y2 -2xy) -2y2  其中x=, y= -1 答案：= x2 -2x2 +6xy +3y2 -6xy -2y2 =  -x2 +y2   当x=,y=-1时 原式=-(-)2 +(-1)2=Could you please           me some           ? A．giving, advices                                        B．give, advices C．give, advice                                                 D．to give, advice