1.（-y)^2×y^n-1
=y^2×y^(n-1)
=y^(2+n-1)
=y^(n+1)
2.(4a^3b-6a^b^2+12ab^3)÷（2ab)
=4a^3b÷（2ab)-6a^2b^2÷（2ab)+12ab^3÷（2ab)
=2a^2-3ab+6b^2