lim(x->+∞)[√(x²+x)-√(x²-x)]=lim(x->+∞)[((x²+x)-(x²-x))/(√(x²+x)+√(x²-x))] (有理化分子)=lim(x->+∞)[2x/(√(x²+x)+√(x²-x))]=lim(x->+∞)[2/(√(1+1/x)+√(1-1...