Let f (x) = ax 2.

Bronx (Bronx)

c，a≠0

f(0)=c=0

c=0

f(x

1)-f(x)=a(x

1)^2

b(x

1)-(ax^2

bx)

=a(2x

1)

b

=2ax

(1)

b)

=2x

a= 1

b=- 1

f(x)=x^2-x；

2.

The image with f (x) = x 2-x is a parabola with vertex (1/2,-1/4) and upward opening.

So as long as y=2x

M is below (1/2,-1/4).

2( 1/2)

m