Which shows a perfect square trinomial?

50 y squared minus 4 x squared
100 minus 36 x squared y squared
16 x squared + 24 x y + 9 y squared
49 x squared minus 70 x y + 10 y squared

65 8 7 4 5 6 8 4 3 2 1 9 5 6 4 2 1 6 5 1 5 1 3 2 3 5 multiply the third number in the first row by the seventh number in the third row. add this result to the fifth number in the second row. add to this total ten times the fourth number in the third row. subtract the eighth number in the first row from the result.

How do i do this activity, is appreciated

Apool measures 12.3 feet by 16.6 feet. if the longer wall of the pool has a diagonal of 17.8 feet, what is the volume of the pool? (round to nearest tenth)