When x=-2 is an equal sign.

2，a2+b2= 1 ≥2ab，x2 + y2 =4≥2xy

2ax+2by≤a2+x2+y2+B2 = 1+4 = 5，ax + by≤5/2

3、a>b>0，a2+B2/2 = 1 a2 = 1-B2/2≥0，b2≤2

a√ 1+B2 =√a2( 1+B2)= √( 1-B2/2)( 1+B2)=√ 1/2(B2 B2+B2+2)≤√( 4+2+2))= 2√2

4, f (x)-x+12= 0 has two real roots, 3 and 4.

f(3) =-9，f(4)=-8，

f(x)= x2/ax+b f(3)= 9/(3a+b)=-9 f(4)= 16/(4a+b)=-8

a= 1/2，b=- 1/2

(1) Find the expression f (x) = 2x2/(x- 1)

(2) let k > 1 and solve the inequality f (x) < (k+ 1) x-k/2-x about x.

2 x2/(x- 1)