A:x2+by+c=0
B:x2+5x=x2+1
C:3y2+y4+6=0
D:x2+x+2x=5
未成年人需要摄人足够的钙促进骨骼的生长.下列食物中钙含量最低的是( )
A.metal glass wool cotton wood
B.earth sheep trees sand plant
已知a≠0,14(a2+b2+c2)=(a+2b+3c)2,那么a:b:c=( )