We can rewrite the expression by multiplying by the conjugate and dividing by the same conjugate:
x2+x−x2−1=(x2+x−x2−1)⋅x2+x+x2−1x2+x+x2−1 =x2+x+x2−1(x2+x)−(x2−1) =x2+x+x2−1x+1 Now, we divide both the numerator and the denominator by x. Since x→∞, we can assume x>0, so x2=x. x2+x+x2−1x+1=xx2+x+xx2−1xx+1=x2x2+x+x2x2−11+x1 =1+x1+1−x211+x1 Now we take the limit as x→∞. limx→∞1+x1+1−x211+x1=1+0+1−01+0=1+11=1+11=21