Lesson 5.3--Part Three--- Solving Quadratic Equations by ...

1 Lesson Three--- Solving Quadratic Equations by Graphing and Factoring When a soccer ball is kicked into the air, how long will the ball take to hit the ground? The height h in feet of the ball after t seconds can be modeled by the Quadratic function h(t) = 16t2 + 32t. In this situation, the value of the function represents the height of the soccer ball. When the ball hits the ground, the value of the function is zero. A zero of a function is a value of the input x that makes the output f(x) equal zero. The zeros of a function are the x . intercepts. 1. Unlike linear functions, which have no more than one zero, Quadratic functions can have two zeros, as shown at right. These zeros are always symmetric about the axis of symmetry.

2 Example: Find the zeros of f(x) = x2 6x + 8 by factoring and by graphing on your calculator. Find the zeros of g(x) = x2 2x + 3 by factoring and by graphing on your calculator The solution to a Quadratic equation of the form ax2 + bx + c = 0 are roots. The roots of an equation are the values of the variable that make the equation true. ROOTS = SOLUTIONS = X INTERCEPTS = ZEROS. All four of these represent the same part of the graph of a Quadratic function. 2. Example: Find the zeros of the function by factoring. g(x) = 3x2 + 18x Example: Find the solutions or roots to the equation by factoring. Check on calculator. 2. 6x +13x 5 = 0.. HW: p. 338 22, 24, 26 28, 30, 31, 34 38, 40, 42, 47, 54, 55, 57, 59, 62, 67 69, 78, 80, 83 85 = 28 problems 3.

3 Any object that is thrown or launched into the air, such as a baseball, basketball, or soccer ball, is a projectile. The general function that approximates the height h in feet of a projectile on Earth after t seconds is given. Note that this model has limitations because it does not account for air resistance, wind, and other real-world factors. Example: A golf ball is hit from ground level with an initial vertical velocity of 80 ft/s. After how many seconds will the ball hit the ground? Look at on Calculator. Example: A football is kicked from ground level with an initial vertical velocity of 48 ft/s. How long is the ball in the air? . 4. Quadratic expressions can have one, two or three terms, such as.

4 16t2, 16t2 + 25t, or 16t2 + 25t + 2. Quadratic expressions with two terms are binomials. Quadratic expressions with three terms are trinomials. Some Quadratic expressions with perfect squares have special factoring rules. Example: Find the roots of the equation by factoring. 4x2 = 25 18x2 = 48x 32 If you know the zeros of a function, you can work backward to write a rule for the function Example: Write a Quadratic function in standard form with zeros 4 and 7.. 5. Example: Write a Quadratic function in standard form with zeros 5 and 5. Lesson Quiz: Find the zeros of each function 1. f(x)= x2 7x 2. f(x) = x2 9x + 20. Find the roots of each equation using factoring. 3. x2 10x + 25 = 0 4.

5 7x = 15 2x2. 5. Write a Quadratic function in standard form with zeros 6 and 1. 6. A rocket is launched from ground level with an initial vertical velocity of 176 ft/s. After how many seconds with the rocket hit the ground? . 6.