7.下列计算正确的是( )
| A. | 2(a-1)=2a-1 | B. | (a+b)(b-a)=b2-a2 | C. | (a+1)2=a2+1 | D. | (-a-b)2=a2-2ab+b2 |
1.
如图所示,将Rt△ABC绕其直角顶点C按顺时针方向旋转90°后得到Rt△DEC,连接AD,若∠BAC=25°,则∠ADE=( )
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| A. | 20° | B. | 25° | C. | 30° | D. | 35° |