2abc=2*1*√17/2=√17
a,b是x^2+px+1=0的2个根,a,b是直角三角形ABC的2直角边
a+b=-p,ab=1,a^2+b^2=c^2=p^2+2p+3
(a+b)^2=p^2
a^2+b^2+2ab=p^2
p^2+2p+3+2*1=p^2
2p=-5
p=-5/2
c=根号[(-5/2)^2-5+3]=根号[25/4-2]=根号(17/4)=√17/2
2abc=2*1*√17/2=√17