Copy and complete each of the Diamond Problems below. The pattern used in the Diamond Problems is shown at right.  

1. 

   Hint (a):

   What two numbers have a product of $0$ and a sum of $25$?

   Answers (a):

   

2. 

   Hint (b):

   $6·?=-30$

   Answers (b):

   

3. 

   Hint (c):

   See the hints for part (b).

4. 

   Hint (d):

   See the hints for part (a).