Math Problem Statement

6. A quadratic function is defined by g(x) = -(x - 2)^2 + 5. (a) What is the vertex of the graph of function g? (b) Does the vertex represent the minimum value or the maximum value of the function? Explain. (c) If you were to shift this graph 3 units left from where it is now, what would be the equation represented by the new graph? 7. The function h defined by h(t) = (50 + 4.9t)(8 - t) models the height, in meters, of an object t seconds after it is dropped from a helicopter. (a) Find or approximate the time when the object hits the ground. Explain or show your reasoning. (b) From what height is the object dropped? Explain or show your reasoning. (c) When will the object reach its maximum height? Explain or show your reasoning.

Solution

Let’s analyze and solve the questions based on the given mathematical problems from the image.


6. Quadratic Function

The function is g(x)=(x2)2+5g(x) = -(x - 2)^2 + 5.

(a) What is the vertex of the graph of function gg?
The vertex form of a quadratic function is written as g(x)=a(xh)2+kg(x) = a(x - h)^2 + k, where the vertex is (h,k)(h, k).
Here:

  • h=2h = 2
  • k=5k = 5
    Thus, the vertex is (2, 5).

(b) Does the vertex represent the minimum value or the maximum value of the function? Explain.
The coefficient of (xh)2(x - h)^2, which is a=1a = -1, is negative. This indicates the parabola opens downward, so the vertex represents the maximum value of the function.


(c) If you were to shift this graph 3 units left from where it is now, what would be the equation represented by the new graph?
To shift the graph 3 units left, replace xx with x+3x + 3 in the equation:
g(x)=(x2+3)2+5g(x) = -(x - 2 + 3)^2 + 5
Simplify:
g(x)=(x+1)2+5g(x) = -(x + 1)^2 + 5

The new equation is g(x)=(x+1)2+5g(x) = -(x + 1)^2 + 5.


7. Helicopter Height Function

The function is h(t)=(50+4.9t)(8t)h(t) = (50 + 4.9t)(8 - t).

(a) Find or approximate the time when the object hits the ground. Explain or show your reasoning.
The object hits the ground when the height h(t)=0h(t) = 0. Set the equation to 0:
(50+4.9t)(8t)=0(50 + 4.9t)(8 - t) = 0
This product is zero if either factor is zero:

  1. 50+4.9t=050 + 4.9t = 0: Solve for tt:
    t=504.910.2t = -\frac{50}{4.9} \approx -10.2 (not valid because t0t \geq 0)

  2. 8t=08 - t = 0: Solve for tt:
    t=8t = 8

Thus, the object hits the ground at t=8t = 8 seconds.


(b) From what height is the object dropped?
The object is dropped at t=0t = 0. Substitute t=0t = 0 into h(t)h(t):
h(0)=(50+4.9(0))(80)=508=400h(0) = (50 + 4.9(0))(8 - 0) = 50 \cdot 8 = 400

The object is dropped from a height of 400 meters.


(c) When will the object reach its maximum height? Explain.
The function h(t)=(50+4.9t)(8t)h(t) = (50 + 4.9t)(8 - t) represents a parabola. The maximum height occurs at the vertex. Rewrite h(t)h(t):
h(t)=4.9t2+(84.950)t+400h(t) = -4.9t^2 + (8 \cdot 4.9 - 50)t + 400
The vertex occurs at t=b2at = -\frac{b}{2a}, where a=4.9a = -4.9 and b=(84.950)b = (8 \cdot 4.9 - 50):
b=39.250=10.8b = 39.2 - 50 = -10.8
t=10.82(4.9)=10.89.81.1secondst = -\frac{-10.8}{2(-4.9)} = \frac{10.8}{9.8} \approx 1.1 \, \text{seconds}

The object reaches its maximum height at approximately 1.1 seconds.


Do you want additional details or explanations?

Here are 5 related questions to extend your learning:

  1. How do you determine the axis of symmetry for a parabola?
  2. Why does a negative coefficient in a quadratic equation indicate a maximum value?
  3. How would the equation change if the graph of g(x)g(x) were shifted 5 units up?
  4. Can you write the factored form of the quadratic height equation h(t)h(t)?
  5. How would air resistance alter the function for the helicopter drop?

Tip: Always analyze the sign of the leading coefficient aa to understand the behavior of a parabola (opening up or down).

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Math Problem Analysis

Mathematical Concepts

Quadratic Functions
Vertex Form
Height Modeling
Parabolas

Formulas

Vertex form of a quadratic function: g(x) = a(x - h)^2 + k
Solving for the time when the height is zero
Quadratic equation for projectile motion

Theorems

Vertex represents the maximum or minimum of a parabola depending on the sign of a
Time of flight for projectile motion

Suitable Grade Level

Grades 8-10