a=n^2-1 b=2n c=n^2+1 三角形ABC是直角三角形吗?

因为a^2=(n^2-1)^2=n^4-2n^2+1,
b^2= (2n)^2=4n^2
c^2=( n^2+1)^2=n^4+2n^2+1
所以(n^4-2n^2+1)+(4n^2)=n^4+2n^2+1
所以a^2+b^2=c^2
所以三角形ABC是直角三角形