15 + 14 = 75×20%= 45 × 716 = 920 × 518 =
3.14×3= 58 ÷ 14 = 15.7÷5= 20÷ 14 =
18 - 116 = 49÷ 714 = 81× 29 = 56× 57 =
1- 25 = 34 + 45 = 84×50%= 25 ×40=
用配方法解方程:x2-4x+2=0,下列配方正确的是( )
组织的形成是( )