SITE-A teams: Lesson 21

Solving an equation of quadratic form can be accomplished graphically using the CASIO fx7400G.

Solve for x: x4 - 13 x2 + 36 = 0

Turn on the CASIO fx7400G.

Use your cursor arrows to highlight the GRAPH menu and press or just press when at the main menu screen.

In the Y1 slot enter the expression X4 - 13 X2 + 36 and press

(Make sure no other Y-slot is highlighted, i.e. selected for graphing.)

Press (V-Window)

Set up the viewing window as follows:

Xmin    -3.9    Ymin:     -23

max:      3.9    max:      23

s c l:        1      s c l:    5

Press

Press (DRAW)

The graph appears on the screen of the calculator. Press (Trace) and use the right cursor arrow to move the "cross hairs" to where the graph crosses the x-axis. This is at the points ( -3, 0 ), ( -2, 0 ), ( 2, 0 ), and ( 3, 0 ). Thus the real-valued solutions are: x = -3, x = - 2, x = 2, and x = 3.

Press

Highlight the expression and de-select it by pressing (SEL) or delete it by pressing (DEL)

Solve for x: x6 + 7 x3 - 8 = 0

In the Y2 slot enter the expression X6 + 7 X3 - 8 and press

(Make sure no other Y-slot is highlighted, i.e. selected for graphing.)

Press (DRAW)

The graph appears on the screen of the calculator. Press (Trace) and use the right cursor arrow to move the "cross hairs" to where the graph crosses the x-axis. This is at ( -2, 0 ) and ( 1, 0). Thus the real-valued solutions are: x = -2 and x = 1.

Press

Highlight the expression and de-select it by pressing (SEL)

or delete it by pressing (DEL)

Solve for x:

In the Y3 slot enter the expression 2 X + 3 Ö X - 2 and press

(Make sure no other Y-slot is highlighted, i.e. selected for graphing.)

Press (V-Window)

Set up the viewing window as follows:

Xmin: -1.95    Ymin: -1.15

max:    1.95     max:      1.15

s c l:     0.5     s c l:      0.5

Press

Press (DRAW )

The graph appears on the screen of the calculator. Press (Trace) and use the right cursor arrow to move the "cross hairs" to where the graph crosses the x-axis. This is at x = 0.25 and y = 0. Thus the real-valued solution is x = 0.25.

Press

Highlight the expression and de-select it by pressing (SEL) or delete it by pressing (DEL)

Press

Turn off the CASIO fx7400G. Press (OFF)