√代表根号
1.(√2+√3)(√2-√3)+2√12
=(√2)*(√2)-(√3)*(√3)+4√3
=2-3+4√3=4√3-1
2.2√5(4√20-3√45+2√5)
=2√5(8√5-9√5+2√5)
=(2√5)*√5=10