Heidi bought a machine that throws tennis balls for her dog to fetch. The height of each ball thrown by the machine, in feet, is modeled by the function f(x) = –x2 + x + 2, where x represents time in seconds. How many seconds after the machine throws the ball does it hit the ground?

2 seconds

Step-by-step explanation:

Given the equation:

Where f(x) represents the height of each ball thrown by machine.

and x represents the time in seconds.

To find:

The number of seconds after which the machine throws the balls hits the ground = ?

Solution:

In other words, we have to find the value of after which the

(Because when the ball hits the ground, the height becomes 0).

Let us put and solve for

sec is not a valid answer because time can not be negative.

So, the answer is after 2 seconds, the ball hits the ground.

step-by-step explanation:

the ratio of red paint to blue paint is always 9/7. that means that, whatever x's value, (4x+12)/(4x-4) has that same ratio. so, set up an equation and cross-multiply to solve for x:

9/7 = (4x+12)/(4x-4)

9(4x-4) = 7(4x+12)

36x - 36 = 28x + 84

8x - 36 = 84

8x = 120

x = 15