12: After substituting the limit point into the given expression you should get
![](gif4/ecb4al1.gif)
Why 0- in the denominator?
As x→(−1) from the
right, one has x > −1, but it is also a negative number
(x is close to −1). Therefore
x2 < 1 (draw a picture) and thus
(1 − x2) < 0.
Answer