Linear functions parabola mostly things in algebra
        
             
        
        
        
Answer:
1 f(n) = 3(5)^x-1
2 f(n) = 40(3/2)^x-1
Step-by-step explanation:
The first number in the sequence, times the (multiplicative factor)^ x-1 is the rule for geometric sequences.
 
        
                    
             
        
        
        
You would divide negative 3 (-3) from both sides to keep the c by itself. When you divide a positive by a negative it becomes negative. 
Dividing 15 by -3 would equal -5, so c = -5
        
             
        
        
        
I hope this helps you 
3x-25=6x-80
6x-3x=80-25
3x=55
x =55/3