— I suppose you are at least 60 years old.— Thank you. I'm glad you______ that. My real age is 62.
二次函数y=﹣x2+2x+4的最大值为( )
(1)某厂房屋顶呈人字架形(等腰三角形),如图1所示,已知AC=BC=8m,∠ACB=120°,CD⊥AB于点D.求AB的长度.
(2)如图2所示,在平行四边形ABCD中,BE、CF平分∠B、∠C,交AD于E、F两点,求证:AF=DE.