The domain of a(x) is all of R. The domain of b is the range where
![x-4 \geq 0, hence \ x \geq 4](https://img.qammunity.org/2019/formulas/mathematics/high-school/7d1wkx6zt9nlhx2j8e7ke3rajah86x4p1k.png)
. We can calculate the composition boa by changing in the expression for b, every x with a(x). Hence, boa(x)=
![√((3x+1)-4)](https://img.qammunity.org/2019/formulas/mathematics/high-school/ul1e7po5aubfdkajc91ghrand8iztgpoq1.png)
=
![√(3x-3)](https://img.qammunity.org/2019/formulas/mathematics/high-school/cck4ce4e25xfsuiw5gmrn804yz8lu2sjs1.png)
. Again for a function with a root to be defined, we need that the expression under the square root has to be positive. Hence, 3x-3
![\geq](https://img.qammunity.org/2019/formulas/mathematics/middle-school/2rr84kwhqyb59wsef29mndhxe1ucuusgtw.png)
0.Thus, the set where this holds is
![3x \geq 3, x \geq 1](https://img.qammunity.org/2019/formulas/mathematics/high-school/vaznmcx4ocafy7llgs48g8xfnjyf8jmz35.png)
. This is also the domain of the function boa(x).