What's Happening
Intersections
Build the Model
Max/Min
Calculator Strategy
100

Graph y = x3 - 6x2 + 9x

How many turning points does the graph have?

2

100

Find intersection:
y=x2, y=4

x = -2, 2

100

Solve by graphing. 

x= 9

x = -3, 3

100

Find max of: 

y = -x2 + 4 

4

100

You graph a function but see nothing. What’s your first move?

Adjust window / use ZStandard

200

Graph y = x4 - 4x2

How many x-intercepts does the graph have?

3

200

Find intersection:
y=x2, y=x+2

x = -1, 2

200

Solve by graphing. 

2x= x + 3

x = -1, 1.5

200

Find min of:

y = x2 - 6x +5

-4

200

How can you find a zero more precisely after estimating with table?

Use CALC → zero

300

Graph y= ln(x) - x + 2

How many real solutions (zeros) does the function have?

1

300

Find intersection:
y=ex, y=3

x = 1.10

300

Solve by graphing. 

sin⁡(x) = 0.3 between [0, 2pi]

x = 0.305, 2.837

300

Find max of:

y = sin(x) + cos(x)

1.414

300

When should you use table instead of graph?

When looking for patterns or approximate values

400

Graph y = xe-x

On what interval is the function increasing?

Increasing from negative infinite to 1

400

Find intersection:
y=ln⁡(x), y=x−2

x = 1.84

400

Solve by graphing. 

ex=2x

x = 1.26

400

Find max of:

y = xe-x

0.368

400

You only see one intersection but expect two. What likely happened?

Window is too small

500

Graph y=sin(x)+x/2

How many solutions does
sin⁡(x)+x/2 =2 have on [0,6]?

1

500

Find all intersections:
y=sin⁡(x), y=0.5x on [0,4]

x = 0, 1.9

500

Solve by graphing. 

x− 3x = 1

  • x≈−1.53
  • x≈0.35
  • x≈1.18
500

Find the x value where: 

y = x3 - 3x has a local minimum

x = 1

500

DAILY DOUBLE

Consider the equations:
y = sin⁡(x) and y = 0.2x2

  1. Graph both functions on [0,4]
  2. Find all points of intersection on this interval.
  3. Determine on which interval(s) sin⁡(x) > 0.2x2
  • Intersections:
    • x=0
    • x≈1.63
  • Comparison:
    • sin⁡(x)>0.2x2 on (0, 1.63)
    • After that, 0.2x2 dominates