The square root of 16 = 4, <em>therefore it is </em><em>not </em><em>an irrational number.</em>
The square root of 7 = 2.64575131106... <em>therefore it </em><em>is</em><em> an irrational number.</em>
823.1 ends at 1, <em>therefore it is </em><em>not</em><em> an irrational number.</em>
-9 does not continue forever, <em>therefore it is </em><em>not</em><em> an irrational number.</em>
8.070070007... continues on forever, <em>therefore it </em><em>is</em><em> an irrational number.</em>
Thus, the irrational numbers here are: √7 and 8.070070007...