a(a-1)-(a^2-b)=-1,a-b=1
(a+b)^2=(a-b)^2+4ab=4
a+b=2或-2
a^4b+ab^4
=ab(a^3+b^3)
=ab(a+b)(a^2-ab+^2)
=ab(a+b)[(a-b)^2+ab]
=±2*3/4*7/4
=±21/8