I think (jk) (x) means j times k
(jk) (x) = -7x(9 - 2x) //Using Distributive Property.
(jk) (x) = -63x + 14x^2 = 14x^2 - 63
//Hope it helps.
 
        
             
        
        
        
X=12 that's is the answers
        
             
        
        
        
Answer:
Step-by-step explanation:
Given equation of the quadratic function is,
y = x² + 5x - 7
Convert this equation into vertex form,
y = x² + 2(2.5x) - 7
   = x² + 2(2.5x) + (2.5)² - (2.5)² - 7
   = (x + 2.5)²- 6.25 - 7
   = (x + 2.5)² - 13.25 
Therefore, vertex of the function is → (-2.5, -13.25)
For the solutions, 
y = 0
(x + 2.5)² - 13.25 = 0
x = (±√13.25) - 2.5
x = (±3.64) - 2.5
x = 1.14, -6.14
Solutions → (-6.14, 0) and (1.14, 0)
  
        
             
        
        
        
Answer:
Best deal is corner store
Step-by-step explanation:
LCM is 480 oz
480 oz of the Vending Machine would be £24 (0.60 x (480/12))
480 oz of the Corner Store would be £22.80 (0.95 x (480/20))
480 oz of Grocery store would be £23.25 (1.55 x (480/32))