1. 7.2 Writing Quadratic Functions and Models
What do you call 2 quadratics who like to go bowling?
A para-bolas

2. Bacteria Growth Which is a Better Fit?
Day (X):
Population (Y): 5 10 15 20 25 30 60
135
240
370
500
740

3. Vocabulary
Quadratic Regression: the process of finding the best-fitting quadratic model for a set of data
Curve Fitting: find a line or curve that matches a set of data points

4. Back to Bacteria
Standard Form:

5. You Try: (QuadReg) (Txtbk p. 256 GP #7) Enter Data L1, L2
STATPLOT “On” (Scatterplot) L1, L2
ZOOM 9
STAT > CALC > 5:
GRAPH (VARS, etc.)

6. A Parabola in Vertex Form:
y = a (x - h)2 +k
What variations of a parabola are there?

7. Write EQ Given Vertex & Point: y = a(x - h)2 +k
Substitute in everything and get “a”!
Then rewrite the equation with x and y (numbers for a, h, k).
Ex: Vertex (-2, 1), point (2, 5)

8. y = a(x – h)2 + k Write a quadratic function in vertex form EXAMPLE 1
Write a quadratic function for the parabola shown.
SOLUTION
Use vertex form because the vertex is given.
y = a(x – h)2 + k
A quadratic function for the parabola is y = (x – 1)2 – 2.

9. GUIDED PRACTICE
Write a quadratic function whose graph has the given characteristics.
1. vertex: (4, –5)
passes through: (2, –1)
y = (x – 4)2 – 5
ANSWER
2. vertex: (–3, 1)
passes through: (0, –8)
ANSWER
y = (x + 3)2 + 1

10. Homework
See Agenda