Answer:
A) [First try is correct for all U1 to U4]
Step-by-step explanation:
1. Trying each option
(let x = 1,2,3,4) since it goes from U1 to U4 (Geometric sequence)
A.) 10(-4/5)^x 
10(-4/5)^1 = -8
10(-4/5)^2 = 6.4
10(-4/5)^3 = -5.12
10(-4/5)^4 = 4.096
 
        
             
        
        
        
Let's take this one at a time starting from the brother's net income because this would be the root basis. We let x be the number of lawns his brother and Tom mowed. 
Brother's Net Income = 32x - 12x = 20x
Mitch promises to pay the borrowed money of $500 plus 40% of what his brother earns. The algebraic equation for this is:
Mitch's payment = $500 + 0.4(20x) = $500 +$8x
        
                    
             
        
        
        
Answer:
 a.  4y =12x  the constant of variation is 3
Step-by-step explanation:
The equation for direct variation is y=kx
 a.  4y =12x
  Divide each side by 4
4y/4 = 12x/4
  y = 3x
This is direct variation and the constant is 3
Equations b ,c, d  all have a constant added which make them something other than a direct variation