如图,在△ABC中,AB=AC=32cm,DE是AB的垂直平分线,分别交AB、AC于D.E两点,BC=21cm,连BE,则△BCE的周长是 cm.
填写解方程3x(x+5)=5(x+5)的过程 解:3x(x+5)__________=0 (x+5) (__________)=0 x+5=__________或__________=0 ∴x1=__________,x2=__________
方程x2-16=0,可将方程左边因式分解得方程__________,则有两个一元一次方程____________或____________,分别解得:x1=__________,x2=__________.
如果两个因式的积是零,那么这两个因式至少有__________等于零;反之,如果两个因式中有__________等于零,那么它们之积是__________.
用配方法使下面等式成立: (1)x2-2x-3=(x-______)2-_______; (2)x2+0.4x+0.5=(x+_______)2+________; (3)3x2+2x-2=3(x+______)2+________; (4)x2+x-2=(x+________)2+_______.
填上适当的数,使下面各等式成立: (1)x2+3x+_______=(x+________)2; (2)_______-3x+=(3x_______)2; (3)4x2+_____+9=(2x________)2; (4)x2-px+_______=(x-_______)2; (5)x2+x+_______=(x+_______)2.