Explanation

If f(x) is continuous at c, find limit by direct substitution:

lim (x → c) f(x) = f(c)

Example:
lim (x → 3) (2x+5) = 2(3)+5 = 11

Quiz

1. When can you use direct substitution?

2. lim (x → 4) (3x−1) = ?

3. Is direct substitution faster than tables?

4. Can you use it when denominator = 0?

5. lim (x → 0) x² = ?

Answer Key

1. f(x) is continuous at c

2. 3×4−1 = 11

3. Yes

4. No

5. 0