Solving Quadratic Equation by Graphing and Factoring Section 6.2& 6.3 CCSS: A.REI.4b
Mathematical Practices: 1. Make sense of problems and persevere in solving them. 2. Reason abstractly and quantitatively. 3. Construct viable arguments and critique the reasoning of others. 4. Model with mathematics. 5. Use appropriate tools strategically. 6. Attend to precision. 7. Look for and make use of structure. 8. Look for and express regularity in repeated reasoning.
CCSS: A.REI.4b 4 SOLVE quadratic equations by inspection (e.g., for x2 = 49), taking square roots, completing the square, the quadratic formula and factoring, as appropriate to the initial form of the equation. RECOGNIZE when the quadratic formula gives complex solutions and write them as a ± bi for real numbers a and b.
Essential Question: 4 How do I determine the domain, range, maximum, minimum, roots, and y-intercept of a quadratic function from its graph & how do I solve quadratic functions by factoring?
Quadratic Equation y = ax 2 + bx + c ax 2__ is the quadratic term. bx--- is the linear term. c-- is the constant term. The highest exponent is two; therefore, the degree is two.
Example f(x)=5x 2 -7x+1 Quadratic term 5x 2 Linear term -7x Constant term 1 Identifying Terms
Example f(x) = 4x 2 - 3 Quadratic term 4x 2 Linear term 0 Constant term -3 Identifying Terms
Now you try this problem. f(x) = 5x 2 - 2x + 3 quadratic term linear term constant term Identifying Terms 5x 2 -2x 3
The number of real solutions is at most two. Quadratic Solutions No solutionsOne solutionTwo solutions
Solving Equations When we talk about solving these equations, we want to find the value of x when y = 0. These values, where the graph crosses the x-axis, are called the x-intercepts. These values are also referred to as solutions, zeros, or roots.
Example f(x) = x 2 - 4 Identifying Solutions Solutions are -2 and 2.
Now you try this problem. f(x) = 2x - x 2 Solutions are 0 and 2. Identifying Solutions
The graph of a quadratic equation is a parabola. The roots or zeros are the x-intercepts. The vertex is the maximum or minimum point. All parabolas have an axis of symmetry. Graphing Quadratic Equations
One method of graphing uses a table with arbitrary x-values. Graph y = x 2 - 4x Roots 0 and 4, Vertex (2, -4), Axis of Symmetry x = 2 Graphing Quadratic Equations xy 00 1-3 2-4 3-3 40
Try this problem y = x 2 - 2x - 8. Roots Vertex Axis of Symmetry Graphing Quadratic Equations xy -2 1 3 4
The graphing calculator is also a helpful tool for graphing quadratic equations. Graphing Quadratic Equations
Roots or Zeros of the Quadratic Equation The Roots or Zeros of the Quadratic Equation are the points where the graph hits the x axis. The zeros of the functions are the input that make the equation equal zero. Roots are 4,-3
To solve a Quadratic Equation Make one side zero. Then factor then set each factor to zero
How to write a quadratic equation with roots Given r 1,r 2 the equation is (x - r 1 )(x - r 2 )=0 Then foil the factors, x 2 - (r 1 + r 2 )x+(r 1 · r 2 )=0
How to write a quadratic equation with roots Given r 1,r 2 the equation is (x - r 1 )(x - r 2 )=0 Then foil the factors, x 2 - (r 1 + r 2 )x+(r 1 · r 2 )=0 Roots are -2, 5 Equationx 2 - (-2+5)x+(-2)(5)=0 x 2 - 3x -10 = 0
How to write a quadratic equation with roots Roots are ¼, 8 Equationx 2 -(¼+8)x+(¼)(8)=0 x 2 -(33/4)x + 2 = 0 Must get rid of the fraction, multiply by the common dominator. 4 4x 2 - 33x + 8 = 0