Find a maximum or minimum
Find the lowest or highest point of a curve, such as the vertex of y = x² − 2x.
The lowest point on a smooth curve is a minimum and the highest is a maximum. For a parabola, this is the vertex.
The example y = x² − 2x has its minimum at (1, -1).
Classic Graphing 84
Start on the main screen: Press 2nd then mode (QUIT) to get back to the home screen. Pressing clear on a menu also backs out of it.
Enter X² − 2X on y= and press graph.
y=X,T,θ,nx²−2X,T,θ,ngraphOpen the CALC menu (2nd then trace) and pick 3, minimum. (4 is maximum.)
2ndCALCtrace3Left bound -5, enter. Right bound 5, enter. Then enter for the guess.
(−)5enter5enterenter
You should seeMinimum X=1 Y=⁻1
Classic Graphing 84 key reference · Classic Graphing 84 manual
Natural Color Graphing
Start on the main screen: Press MENU then 1 to open Run-Matrix, the main calculation screen. Press EXIT to back out of a bar or screen, and SHIFT then EXIT (QUIT) to return to the app start.
Enter X² − 2X in the Graph app and draw it with F6.
MENU3X,θ,Tx²−2X,θ,TEXEF6Open G-SOLV (F5) and press F3 for MIN. (F2 is MAX.)
F5F3
You should seeMIN X=1 Y=-1
Natural Color Graphing key reference · Natural Color Graphing manual
Classic CAS
Start on the main screen: Press home to open the Home menu (Calculator, Graphs, Settings, and more). Choose Calculator, or press esc to go back to the calculation page.
Graph x² − 2x. The ² key gives a power and the multiplication dot is implied between 2 and x.
docxx²−2xenterOpen the menu, choose 4, Analyze Graph, then 2, Minimum. (3 is Maximum.)
menu42
You should seeminimum x=1 y=-1
Tips
- A parabola that opens upward has a minimum. One that opens downward has a maximum.
- Choose bounds that surround only one turning point.