原式=lim(x→正无穷)根号(x+a)(x-b)-x=lim(x→正无穷)x[根号(1+(a-b)/x-ab/x^2)-1]因为x→正无穷所以1/x→0运用等价无穷小lim(x→正无穷)x[根号(1+(a-b)/x-ab/x^2)-1]=lim(x→正无穷)x((a-b)/x-ab/x^2)/2=lim(x→正...
