Answer:
i. 9
ii. 14
iii. 405
iv. 
Step-by-step explanation:
The number of diagonals in a polygon of n sides can be determined by:

where n is the number of its sides.
i. For a hexagon which has 6 sides, 
number of diagonals = 
                                    = 
                                    = 9
The number of diagonals in a hexagon is 9.
ii. For a heptagon which has 7 sides, 
number of diagonals = 
                                    = 
                                    = 14
The number of diagonals in a heptagon is 14.
iii. For a 30-gon;
number of diagonals = 
                                           = 
                                          = 405
The number of diagonals in a 30-gon is 405.
iv. For a n-gon,
number of diagonals = 
The number of diagonals in a n-gon is 
 
        
             
        
        
        
You’re answer is y=-1/1.5x+2.5 
Explanation
2.5 is you’re y intersect and you go over one < and up 1.5
        
             
        
        
        
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