Awater balloon is 5 feet above the ground when sally launches it into the air. use the quadratic equation 0 = -t^2 + 4t + 5 to find how much time, t, it takes for the water balloon to reach the ground.

Step-by-step explanation:

we have

Solve the quadratic equation to find the zero's or x-intercepts

Remember that

The x-intercepts are the values of x when the value of y is equal to zero ( water balloon reach the ground)

we know that

The formula to solve a quadratic equation of the form is equal to

in this problem we have

so

substitute in the formula

therefore

the solution is

b

step-by-step explanation:

if the eqn of the parabola is f(x) = (x-4)(x+2), we need to mult. this out to find the coordinates of the vertex.

then f(x) = x^2 + 2x - 4x - 8, and f(x) = x^2 - 2x - 8.

one way in which you can find the vertex is to calculate x = -b / (2a).   here, that comes to

        )

x = = 1.   f(1) = 1^2 - 2(1) - 8 = - 9.   vertex is at (1, -9).

        2(1) 

find another point on the curve:   let x=0, for which y=-8.   then (0, -8) is on the curve.   plot the vertex and this point and draw a smooth parabola thru both.

hope this