Determine the domain and the range of the function

x*2   -  8x

The domain is all real numbers  

This is a parabola that turns upward

The  x coordinate of the  vertex =   8/ (2*1)   8/2  = 4

And the y coordinateof the vertex  is   4^2 - 8(4)  =  16 -32 =  -16

So...the range is [-16,  infinity )