e^(x^2)-1=x^2+x^4/2+o(x^4), 2cosx-2=-x^2+x^4/12+o(x^4)
e^(x^2)+2cosx-3=x^2+x^4/2+o(x^4)-x^2+x^4/12+o(x^4)=7x^4/12+o(x^4)
xsinx=x(x-x^3/6)+o(x^4), x^2cosx=x^2(1-x^2/2)+o(x^4)
xsinx-x^2cosx=-x^4/6+x^4/2+o(x^4)=x^4/3+o(x^4)
原式=lim(7x^4/12+o(x^4))/(x^4/3+o(x^4))=7/4