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题型:填空题 题类:易错题 难易度:普通
①(3a+4)(3a﹣4)=9a2﹣4;
②(2a2﹣b)(2a2+b)=4a2﹣b;
③(3﹣x)(x+3)=x2﹣9;
④(﹣x+y)(x+y)=﹣(x﹣y)(x+y)=﹣x2﹣y2 .
⑤(3﹣x)2=(x﹣3)2=x2﹣6x+9.
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