(√12-√20)(√15+5)-(√10-√2)²
=（2√3-2√5)[√(3×5)+√√5²]-2(√5-1)²
=2(√3-√5)*√5(√3+√5)-2(6-2√5)
=2√5(3-5)-12+4√5
=-4√5+4√5-12
=-12