Analysis

Note that as x gets larger, reciprocals of positive powers of x get smaller and smaller, getting closer and closer to zero. In fact, we can get them as close to zero as we like, by making x large enough:

x = 10 1,000 1,000,000
1
x = 0.1 0.001 0.000001
1-
x2 =0.010.0000010.000000000001

or, as x →-∞

x = -10 -1,000 -1,000,000
1
x = -0.1 -0.001 -0.000001
1-
x2 =0.010.0000010.000000000001

The third line is the result of our analysis of the components of line 2.

           2                    2      1-       -1   2x2   x-
 lim  1---2x-+-x-  =   lim  1--2x--+-x-⋅-x2-=  lim  x2--2-x2-+--x2
x→ ∞   x2 - 4        x→ ∞   x2 - 4     1x2-  x→ ∞    xx2 - 4x2
                          -1 - 2+ 1
                  =   lim  x2----4-x-
                     x→ ∞   1-  x2
                     0---2+--0
                  =    1 - 0
                  =  - 2

because, as x →∞, -1
x2 0, 2 2, -1
x 0, 1 1, and -4
x2 0.

See another example worked out.

Return to the computation page.

Return to the Limits at Infinity page.