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七年级下数学课件课外练习1_乘法公式_苏科版
1.指出下列各式中的错误,并加以改正: (1)(-a-1)2 = -a2-2a-1; (2) (2a+1)2 =4a2+1; (3)(2a-1)2 =2a2-2a+1. 解:(1) (-a-1)2 = [-(a+1)]2 = (a+1)2 = a2+2a+1; 解:(2) (2a+1)2 =(2a)2+2·(2a)·1+12 =4a2+4a+1; 1.指出下列各式中的错误,并加以改正: (1)(-a-1)2 = -a2-2a-1; (2) (2a+1)2 =4a2+1; (3)(2a-1)2 =2a2-2a+1. 解:(3) (2a-1)2 =(2a)2-2·(2a) ·1+12 =4a2- 4a+1. 1.指出下列各式中的错误,并加以改正: (1)(-a-1)2 = -a2-2a-1; (2) (2a+1)2 =4a2+1; (3)(2a-1)2 =2a2-2a+1.查看更多