The other one is 4 root numbers 2.

2.y =(- 14/3)x- 1 1/3

3.s6 minimum s6=-66

4.cosc=(a^2+b^2-c^2)/(2ab)=[(a+b)^2-2ab-c^2]/(2ab)

=[(a+b)^2-c^2]/(2ab)- 1

Because (a-b) 2 ≧ 0, (a+b) 2 ≧ 4ab.

cosc≦[(a+b)^2-c^2]/[0.5*(a+b)^2]- 1= 1-(2c^2)/(a+b)^2

Because a+b≧2c, (a+b) 2 ≧ 4c 2.

So cosc ≦1-0.5 * (4c2)/(a+b) 2 ≦1/2.

So ∠ c ≦ 60