题目

先化简,在求值: ,其中 答案：解： 原式=2x2-2x+4y-2x2+2y=-2x+6y当x=-1，y=2时原式=-2×（-1）+6×2=2+12=14It is very merciless _____ you to have _______ the homeless tramp in a worn-out coat when he begged something to eat. A. to; turned off　　 B. for; turned down　 C. with; turned up　　 D. of; turned away