Which of the following is NOT true?

Question

• $(a^+)^∗=(a^∗)^+$

• $(a^+)^+=aa^+$

• $(a^∗)^∗=a^∗$

• $aa^+ +a=a^+$

Answer 1

....

Answer 2

$(a^{+})^{+} \not\equiv aa^{+}$

because the smallest string generated by $(a^{+})^{+}$ is $'a'$ and the smallest string generated by $aa^{+}$ is $'aa'$.

Answer 3

No...Because (a*+b*) can not generate ab,ba....Etc.