Pls Help On Math Quiz! Will give brainlest and like :P

What is the missing constant term in the perfect square that starts with x^2 -20x

Prove the divisibility of the following numbers: 25^9 + 5^7 is divisible by 30.also, read as (25 to the power of 9) + (5 to the power of 7) is divisible by 30. blank x 30what is the blank? ( it should be expressed in exponent form)

Solve this problem! extra ! 3025/5.5 = a/90.75