Domain of definition

X pointing

Value range

range

Point to the change of x, the range of y,

such as

y=ax？ +bx+c=a(x+b/2a)？ +(4ac-b？ )/4a

When a>0 o'clock

The domain of X is R, and the range has the minimum value =(4ac-b? )/4a

When a<0 o'clock

The domain of x is r, and the range has the maximum value =(4ac-b? )/4a

It can be understood as: the activity range of X is the domain, and the range of values obtained by Y through the change of X. ..