F(x) = x (x^3 - x^2 + x + 1)
        
             
        
        
        
If you do width times length you will get 30. Good luck
 
        
             
        
        
        
7720 + 80x = 3200 + 120x
I think this is correct.  Hope it helps!
        
             
        
        
        
Answer:
<h2>
            aₙ = 7n - 10</h2>
Step-by-step explanation:
The nth term:  
So:
     a₄ = a₁ + 3d
18 =  a₁ + 3d   ⇒   3d =  18 - a₁
     a₇ = a₁ + 6d
39 = a₁ + 6d 
39 = a₁ + 2(18 - a₁)
39 = a₁ + 36 - 2a₁
39 = 36 - a₁
a₁ = -3
3d = 18 - (-3)
3d = 21
d = 7
So the nth term:
                             