# Exercises for Section 2.2
### 2.2.1
Consider the context-free grammar:
S -> S S + | S S * | a
1. Show how the string `aa+a*` can be generated by this grammar.
2. Construct a parse tree for this string.
3. What language does this grammar generate? Justify your answer.
#### Answer
1. `S` -> `S` S * -> `S` S + S * -> a `S` + S * -> a a + `S` * -> a a + a *
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