Presentation on theme: "Do Now Factor completely and solve. x2 - 15x + 50 = 0"— Presentation transcript:
1 Do Now Factor completely and solve. x2 - 15x + 50 = 0
2 5.2 Polynomials, Linear Factors, and Zeros Learning Target: I can analyze the factored form of a polynomial and write function from its zeros
3 Polynomials and Real Roots Relative MaximumPOLYNIOMIAL EQUIVALENTSRootsZerosSolutionsX-InterceptsRelative MaximumRelative MinimumRelative MinimumROOTS !
4 Linear FactorsJust as you can write a number into its prime factors you can write a polynomial into its linear factors. Ex. 6 into 2 & 3 x2 + 4x – 12 into (x+6)(x-2)
5 We can also take a polynomial in factored form and rewrite it into standard form. Ex. (x+1)(x+2)(x+3) = foil distribute (x2+5x+6)(x+1)=x (x2+5x+6)+1 (x2+5x+6) = x3+6x2+11x+6 Standard form
6 We can also use the GCF (greatest common factor) to factor a poly in standard form into its linear factors. Ex. 2x3+10x2+12x GCF is 2x so factor it out. We get 2x(x2+5x+6) now factor once more to get 2x(x+2)(x+3) Linear Factors
7 The greatest y value of the points in a region is called the local maximum. The least y value among nearby points is called the local minimum.
8 TheoremThe expression (x - a) is a linear factor of a polynomial if and only if the value a is a zero (root) of the related polynomial function. If and only if = the theorem goes both ways If (x – a) is a factor of a polynomial, then a is a zero (solution) of the function. and Ifa is a zero (solution) of the function then (x – a) is a factor of a polynomial,
9 Zeros A zero is a (solution or x-intercept) to a polynomial function. If (x – a) is a factor of a polynomial, then a is a zero (solution) of the function.If a polynomial has a repeated solution, it has a multiple zero.The number of repeats of a zero is called its multiplicity.
10 A repeated zero is called a multiple zero A repeated zero is called a multiple zero. A multiple zero has a multiplicity equal to the number of times the zero occurs. On a graph, a double zero “bounces” off the x axis. A triple zero “flattens out” as it crosses the x axis.
11 Write a polynomial given the roots 0, -3, 3 Put in factored formy = (x – 0)(x + 3)(x – 3)y = (x)(x + 3)(x – 3)y = x(x² – 9)y = x³ – 9x
12 Write a polynomial given the roots 2, -4, ½ Note that the ½ term becomes (x-1/2). We don’t like fractions, so multiply both terms by 2 to get (2x-1)Put in factored formy = (x – 2)(x + 4)(2x – 1)y = (x² + 4x – 2x – 8)(2x – 1)y = (x² + 2x – 8)(2x – 1)y = 2x³ – x² + 4x² – 2x – 16x + 8y = 2x³ + 3x² – 18x + 8
13 Write the polynomial in factored form. Then find the roots Write the polynomial in factored form. Then find the roots. Y = 3x³ – 27x² + 24xY = 3x³ – 27x² + 24xY = 3x(x² – 9x + 8)Y = 3x(x – 8)(x – 1)ROOTS?3x(x – 8)(x – 1) = 0Roots = 0, 8, 1FACTORED FORM
14 What is Multiplicity?Multiplicity is when you have multiple roots that are exactly the same. We say that the multiplicity is how many duplicate roots that exist.Ex: (x-2)(x-2)(x+3)Ex: (x-1)4 (x+3)Ex: y =x(x-1)(x+3)Note: two answers are x=2; therefore the multiplicity is 2Note: four answers are x=1; therefore the multiplicity is 4Note: there are no repeat roots, so we say that there is no multiplicity
15 Let’s Try OneFind any multiple zeros of f(x)=x4+6x3+8x2 and state the multiplicity
16 Let’s Try OneFind any multiple zeros of f(x)=x4+6x3+8x2 and state the multiplicity
17 Equivalent Statements about Polynomials -4 is a solution of x2+3x-4=0-4 is an x-intercept of the graph of y=x2+3x-4-4 is a zero of y=x2+3x-4(x+4) is a factor of x2+3x-4These all say the same thing
18 Example 1We can rewrite a polynomial from its zeros. Write a poly with zeros -2, 3, and 3 f(x)= (x+2)(x-3)(x-3) foil = (x+2)(x2 - 6x + 9) now distribute to get = x3 - 4x2 - 3x + 18 this function has zeros at -2,3 and 3
19 Polynomials and Linear Factors Write a polynomial in standard form with zeros at 2, –3, and 0.2 –3 0 Zerosƒ(x) = (x – 2)(x + 3)(x) Write a linear factor for each zero.= (x – 2)(x2 + 3x) Multiply (x + 3)(x).= x(x2 + 3x) – 2(x2 + 3x) Distributive Property= x3 + 3x2 – 2x2 – 6x Multiply.= x3 + x2 – 6x Simplify.The function ƒ(x) = x3 + x2 – 6x has zeros at 2, –3, and 0.
20 Polynomials and Linear Factors Find any multiple zeros of ƒ(x) = x5 – 6x4 + 9x3 and state the multiplicity.ƒ(x) = x5 – 6x4 + 9x3ƒ(x) = x3(x2 – 6x + 9) Factor out the GCF, x3.ƒ(x) = x3(x – 3)(x – 3) Factor x2 – 6x + 9.Since you can rewrite x3 as (x – 0)(x – 0)(x – 0), or(x – 0)3, the number 0 is a multiple zero of the function, with multiplicity 3.Since you can rewrite (x – 3)(x – 3) as (x – 3)2, the number 3 is a multiplezero of the function with multiplicity 2.
22 Finding local Maximums and Minimum Find the local maximum and minimum of x3 + 3x2 – 24xEnter equation into calculatorHit 2nd TraceChoose max or minChoose a left and right bound and tell calculator to guess