A method for breaking up a quadratic equation in the form ax 2 + bx + c into factors (expressions which multiply to give you the original trinomial). Use Algebra tiles to help you develop the patterns in factoring.
x 2 + 5x + 4 x 2 + 7x + 12 x 2 + 6x + 8
x 2 – 6x + 8 x 2 - 9x + 20 x 2 – 4x + 4 Notice how the answer changes if the b term is negative.
x 2 + 4x – 12 x 2 + 3x – 18 x 2 – 7x – 8 x 2 – 3x – 10
Factor each of the following expressions. x x + 48 x 2 – 22x – 48 x 2 – 13x + 42 x 2 + 5x - 24
Difference of squares a 2 – b 2 = (a + b)(a – b) Examples x 2 – 49 = (x + 7)(x – 7) 4x 2 – 1 = (2x + 1)(2x – 1) Practice Factor: x 2 – 64 Factor: 9x
Check to see if each term in the expression has a common factor. Examples: 8x 3 – 50x What factors do they have in common? 2x(4x 2 – 25) 2x(2x + 5)(2x – 5) Factor the following 5x 4 – 10x 3 2x x + 96
1. Try to factor out a common monomial factor from all terms first. 2. Then look to see if the difference of squares format exists. 3. Use your techniques for factoring a quadratic trinomial if applicable. Do-Now: Factor the following…. 2x 2 – 18x + 40 3x 3 – 9x 2 – 30x
What makes this expression more difficult to factor than what we have done before? 2x 2 + 7x + 6 You can use guess and check using FOIL, but it can become tedious for more difficult problems. Try these using guess and check. 3x 2 – 10x + 8 6x 2 + x – 15
You may want to use this method on more complicated examples, such as…….. 6x 2 + x – 12 First identify the values of a and c. ▪ a = 6, c = -12 Next, multiply a times c. ▪ (6)(-12) = -72 Then find two numbers that multiply to be (a)(c) and add to be the value of b. ▪ (9)(-8) = -72, = 1
Now rewrite the original expression with the x-term written as the sum of the two numbers you found. 6x 2 + x – 12 ▪ 6x 2 – 8x + 9x – 12 Finally, break the expression into two parts and factor twice. (6x 2 – 8x) + (9x – 12) 2x(3x – 4) + 3(3x – 4) (3x – 4)(2x + 3)
2x 2 + 5x – 3 9x x + 4 12x x + 6 15x 2 + 8x – 16 20x 2 – 54x + 36
It allows us to solve: ax 2 + bx + c = 0 using the “Zero Product Property” If the product of two expressions is equal to zero, then……… one or both of the expressions must equal zero. Examples. Solve the following equations. x 2 – x – 42 = 0 x 2 = 7x
Factor: 3x x + 10 8x 2 + 4x – 24 Solve the following equation. 4x x – 24 = 0
When you solve y = ax 2 + bx + c when y = 0, you are finding the roots or zeros of the function. These are the points where the parabola crosses the x-axis.