Помогите найти пределы функции

Ответ. Lim(x^4+x^3+3)/(3*x^4+6*x)=Lim(x^4*(1+1/x+3/(x^4))/(x^4*(3+6/(x^3))=1/3;
Lim(((x-1)^0,5-3)*((x-1)^0,5+3))/(x-10)*(((x-1)^0,5+3))=Lim(x-10)/(x-10)*(((x-1)^0,5+3))=Lim1/((x-1)^0,5+3))=1/9;
Lim(x^2+4*x-21)/(x^2-49)=Lim((x+7)*(x-3))/((x+7)*(x-7))=Lim(x+3)/(x-7)=2/7;