What is the x-coordinate of the vertex of the parabola whose equation is y=3×^2+9×​

Step-by-step explanation:

y = 3x² + 9x

= 3(x² + 3x)

= 3(x² + 3x + 1.5²) -3·1.5²

= 3(x+1.5)² - 6.75

vertex (-1.5, -6.75)

mr. flanders’ class sold 47 doughnuts and   mr. rodriquez’s class sold 38 cartons of milk

step-by-step explanation:

let x be the number of doughnuts sold by mr. flanders’ class and y be the number of cartons sold by mr. rodriquez’s class.

1. together, the classes sold 85 items, then

x+y=85.

2. both classes earn earned $104.49 for their school. if doughnuts were sold for $1.35 each, then x doughnuts costed $1.35x. if cartons of milk were sold for $1.08 each, then y cartons costed $1.08y. hence,

1.35x+1.08y=104.49.

3. solve the system of two equations: