7.
小翠利用如图①所示的长为a、宽为b的长方形卡片4张,拼成了如图②所示的图形,则根据图②的面积关系能验证的恒等式为( )
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| A. | (a-b)2+4ab=(a+b)2 | B. | (a-b)(a+b)=a2-b2 | C. | (a+b)2=a2+2ab+b2 | D. | (a-b)2=a2-2ab+b2 |