Answer: The required sum is
![13y\sqrt a.](https://img.qammunity.org/2019/formulas/mathematics/college/kh9kfjn7b3n8qg7ngdmr9grnkv1ik6huzo.png)
Step-by-step explanation: We are given to find the sum of the following two radical expressions:
![E_1=6y√(a),\\\\E_2=7y√(a).](https://img.qammunity.org/2019/formulas/mathematics/college/lhqob7hntucztfbgj5ohztx5waxy1xywah.png)
Since both the expressions involve the same radical term, so we can simply take the radical term common and add the rest of the terms to get the result.
The summation is as follows:
![S\\\\=E_1+E_2\\\\=6y√(a)+7y√(a)\\\\=(6y+7y)√(a)\\\\=13y√(a).](https://img.qammunity.org/2019/formulas/mathematics/college/atlved9wgme3hyk2wzpv2ng5cp42k4l470.png)
Thus, the required sum is
![13y\sqrt a.](https://img.qammunity.org/2019/formulas/mathematics/college/kh9kfjn7b3n8qg7ngdmr9grnkv1ik6huzo.png)