Simplify the fraction below::
a4+1-2a21-a-a2+a3
a4+1-2a21-a-a2+a3=
a4-2a2+1a3-a2-a+1
=(a2-1)2a2(a-1)-1(a-1)
=a2-12a-1·a2-1
=a2-12a-1·a-1a+1
=a2-12a-1·a+1a-1
=a2-12a2-1a-1
=a2-1·a2-1a2-1a-1
=a2-1a-1
=a-1·a+1a-1
=a+1
a±b2=a2±2·a·b+b2
a2-b2=a-b·a+b
a+1