It was time for class. Mr. King asked all the children __________ down quietly.
A:sit
B:sat
C:to sit
D:sitting
①2cos30°+|﹣3|﹣ 3 (2010﹣π)0+(﹣1)2011
②sin230°+sin45°tan60°+cos230°﹣tan30°.
已知方程x2﹣5x﹣1=0的两根分别为x1与x2,则2x12﹣x1x2+2x22=( )