I really need help with my math homework

Question

1)The height y (in feet) of a ball thrown by a child is y=−1/12x^2+6x+3where x is the horizontal distance in feet from the point at which the ball is thrown. (a) How high is the ball when it leaves the child's hand? (Hint: Find y when x=0)Your answer is y=__

b)what is the maximum height of the ball

C) how far from the cold does the ball strike the ground

Answer 1

Part a...How high is the ball when it leaves the child's hand (x = 0)

Plug 0 in for x and you are left with 0 + 0 + 3 or just 3 feet

Part b...Maximum height of ball. This is a quadratic equation and the x value of the vertex of the parabola is -b/2a where a is the coefficient of the 2nd degree term and b is the coefficient of the 1st degree term.

so we have -6 divided by 2(-1/12) or -6 divided by -1/6. This equals 36. Now substitute this value of x into our equation to get the y value of the vertex. We get -1/12*36^2 + 6*36 + 3 or -108 + 216 + 3 or 111 feet.

Part c...How far from the child does the ball land? Set y = 0

0 = -1/12x^2 +6x +3

Solve using the quadratic formula (-b + or - the square root of (b^2 -4ac))/2a where a is the coefficient of the 2nd degree term, b is the coefficient of the 1st degree term and c is the constant

We get x = -0.5 feet and 72.5 feet. Reject the negative answer.

The correct answer is 72.5 feet.