21: After substituting the limit point into the given expression you should get

Remark: The 0⁺ can be seen like this: Instead of substituting to the original quadratic polynomial, substitute into its factorization (x − 3)⋅(x + 1). You get 0⁺⋅4 = 0⁺.

Hint on limit at −∞
Hint on limit at −3 from the left
Hint on limit at ∞
Answer