GRE考试

【单选题】



网考网参考答案：D
网考网解析：
Since ab≠0, neither a nor b is 0 [KEY FACT A3]. If a and b are each 1, then Column A = 4, and Column B = 0; if, how-ever, a = 1 and b = -1, then Column A = 0 and Column B = 4. Neither column is always greater, and the two columns are not always equal (D). **Column A = a 2 + 2ab + b 2 . Column B = a 2 -2ab + b 2 . After subtracting a 2 + b 2 from each column, we have to compare 2ab and -2ab: either one could be positive and the other negative. document.getElementById("warp").style.display="none"; document.getElementById("content").style.display="block"; 查看试题解析出处>>