The equation $y = -4.9t^2 + 42t + 18.9$ describes the height (in meters) of a ball tossed up in the air at 42 meters per second from a height of 18.9 meters from the ground, as a function of time in seconds. In how many seconds will the ball hit the ground?

9 seconds

Step-by-step explanation:

y = -4.9t² +42t +18.9

if the ball will be on the ground then y =0 and we need to find t by solving the quadratic equation

-4.9t² +42t +18.9 = 0

t= (-b±√b²-4ac)/2a, quadratic formula

t= {-42±√[42²-4*(-4.9)(18.9)] }/ 2(-4.9) , use calculator to solve

t= (-42 ±√2134.44)/ -9.8, solve the square root

t= (-42 ±46.2)/-9.8

one t = (-42 - 46.2)/-9.8 = - 88.2/ -9.8 = 9 seconds

another t = (-42 + 46.2)/-9.8 = 4.2 / -9.8 ≈ - 0.43 seconds reject this answer

answer: the price of one pound cabbage = $ 0.8

the point (10,8) represents that the cost of 10 pounds cabbage is $ 8

step-by-step explanation:

since, here is a proportional relation between the number of pounds of cabbage (x) and the price in dollars (y).

therefore, we can write,

⇒ y = k x

where k is the constant of proportionality.

now, point (5,4) is in the line.

thus, it will satisfies the above equation of line.

⇒ 4 = 5 k

⇒ k = 0.8

thus, the equation of the line is,

y = 0.8 x

a) for x = 1,

y = 0.8

therefore, the cost of one pound of cabbage is 0.8 dollars.

b) in the below graph (10,8) represents that the cost of 10 pounds of cabbage is 8 dollars.