Download - Jan. 13 polynonial sketching
Polynomial Curve Sketching
Warm up
(a) Determine the value of b.
When the polynomial 2x + bx - 5 is divided by x - 3, the remainder is 7.2
Warm up
(a) x + 5x + 2x - 8 = 03 2
Solve by factoring the polynomial completely.
Use your TI 83 to find the roots of the polynomial. x3 - 2x2 - 5x + 6
Answer x = -2, 1, 3
Degree n of a polynomial is odd
The function has opposite behaviour
If the leading coefficient is >0
The graph rises to the right and falls to the left
If the leading coefficient is <0
The graph rises to the left and falls to the right
x3+2x
2+1
-2x3+2x
2+1
When the degree n of a polynomial is even, then the graph has similar behaviour on the left as on the right
If the leading coefficient >0 the graph rises on the left and rises on the rightx
4 + x
3 - 2x
2 + x + 1
If the leading coefficient <0 the graph falls on the left and falls on the right
-x4 - 2x3 + 2x2 + x + 1
Graphing Polynomial Functions
Appearance
Where n is even, the graph looks like this:
ƒ(x) = xn
Where n is odd, the graph looks like this:
Graphing Polynomial Functions
The maximum number of roots for any polynomial function is equal to the degree of the function.
Roots
Examples:
max. # of roots 3 4 5
ƒ(x) = x ƒ(x) = x ƒ(x) = x 3 4 5
Cubic Quartic Quintic
Graphing Polynomial Functions
Sketching
Step 1: Find the y-intercept (let x = 0)
Step 4: Sketch the graph
Step 3: Determine the sign of the function over the intervals defined by the roots.
Step 2: Find all roots. (Use rational roots theorem if necessary.)
Factor the polynomial completely. Sketch the graph.ƒ(x) = x + 5x + 2x - 8 3 2
Sketch the graph of