Casio FX-9750G User manual

Equation Calculations
Your graphic calculator can solve the following three types of equa-
tions:
•Linear equations with two to six unknowns
•Quadratic equations
•Cubic equations
7-1 Before Beginning an Equation Calculation
7-2 Linear Equations with Two to Six Unknowns
7-3 Quadratic and Cubic Equations
7-4 What to Do When an Error Occurs
Chapter
7

116
7-1 Before Beginning an Equation Calculations
Before beginning an equation calculation you have to first enter the correct mode,
and you must also clear the equation memories of any data that might be left over
from a previous calculation.
kk
kk
kEntering an Equation Calculation Mode
Highlight the EQUA icon on the Main Menu and then press w.
1(SIML) ....... Linear equation with two to six unknowns
2(POLY) ...... Quadratic or cubic equation
kk
kk
kClearing Equation Memories
After entering an equation calculation mode (SIML or POLY), clear the calculation
memory for that mode. In the case of SIML, use the function keys to specify the
number of unknowns, from two (1) to six (5). In the case of POLY, use the func-
tion keys to specify either two (1) or three (2) polynomials.
2(DEL)
Press 1(YES) to clear the equation memories of that mode (SIML or POLY), or
6(NO) to abort the clear operation without clearing anything.
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117
7-2 Linear Equations with Two to Six Unknowns
You can use the procedures described here to solve linear equations with unknowns
that match the following formats:
Two unknowns a1x + b1y = c1
a2x + b2y = c2
Six unknowns a1x + b1y + c1z + d1t + e1u + f1v = g1
a2x + b2y + c2z + d2t + e2u + f2v = g2
a3x + b3y + c3z + d3t + e3u + f3v = g3
a4x + b4y + c4z + d4t + e4u + f4v = g4
a5x + b5y + c5z + d5t + e5u + f5v = g5
a6x + b6y + c6z + d6t + e6u + f6v = g6
• You can also solve linear equations with three, four, and five unknowns. In each
case, the format is similar to those shown above.
kk
kk
kEntering the Linear Equation Mode for Two to Six
Unknowns
While the Equation Mode is displayed, press 1(SIML).
1(SIML)
1(2) ............. Linear equation with two unknowns
2(3) ............. Linear equation with three unknowns
3(4) ............. Linear equation with four unknowns
4(5) ............. Linear equation with five unknowns
5(6) ............. Linear equation with six unknowns
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118
kk
kk
kSolving Linear Equations with Three Unknowns
Example To solve the following linear equations for x, y, and z:
4x+y–2z=–1
x+6y+3z=1
–5x+4y+z=–7
While in the Linear Equation Mode (SIML), press 2(3), because the linear equa-
tions being solved have three unknowns.
2(3)
Input each coefficient.
ewbw-cw
-bw
bwgwdwbw
-fwewbw
-hw
Each time you press w, the input value is registered in the highlighted cell. Each
press of winputs values in the following sequence:
coefficient a1→coefficient b1→coefficient c1→coefficient d1→
coefficient a2→coefficient b2→coefficient c2→coefficient d2→
coefficient a3→coefficient b3→coefficient c3→coefficient d3
• You can input fractions and value memory contents as coefficients.
After inputting the coefficients, solve the equations.
1(SOLV)
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7 - 2 Linear Equations with Two to Six Unknowns
Highlighted solution cell value
Value being input into highlighted cell
Coefficient input cells

119
• Internal calculations are performed using a 15-digit mantissa, but results are dis-
played using a 10-digit mantissa and 2-digit exponent.
• This unit performs simultaneous linear equations by placing the coefficients in-
side of a matrix. Because of this, as the coefficient matrix approaches zero, pre-
cision in the inverse matrix is reduced and so precision in the results produced
also deteriorates. For example, the solution for a linear equation with three un-
knowns would be calculated as shown below.
xa1b1c1
–1 d1
y=a2b2c2d2
za3b3c3d3
• An “Ma ERROR” occurs whenever the unit is unable to solve the equations.
• Pressing 1(REPT) returns to the initial display of the Linear Equation Mode.
Depending on the coefficients that you use, it may take considerable time for
the calculation result of simultaneous linear equations to appear on the dis-
play. Failure of a result to appear immediately does not mean that the unit is
not functioning properly.
kk
kk
kChanging Coefficients
You can change a coefficient either before or after you register it by pressing w.
uu
uu
uTo change a coefficient before registering it with ww
ww
w
Press the Akey to clear the current value and then input another one.
uu
uu
uTo change a coefficient after registering it with ww
ww
w
Use the cursor keys to highlight the cell that contains the coefficient that you want to
change. Next, input the value that you want to change to.
kk
kk
kClearing All the Coefficients
While in the Linear Equation Mode, press the 3(CLR) function key. This operation
clears all the coefficients to zero.
3(CLR)
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Linear Equations with Two to Six Unknowns 7 - 2

120
7-3 Quadratic and Cubic Equations
This calculator can also solve quadratic and cubic equations that match the following
formats (when aGG
GG
G0):
• Quadratic: ax2+ bx + c= 0
• Cubic: ax3+ bx2+ cx + d= 0
kk
kk
kEntering the Quadratic/Cubic Equation Mode
While in the Equation Mode, press 2(POLY).
2(POLY)
1(2) ............. Quadratic equation
2(3) ............. Cubic equation
kk
kk
kSolving a Quadratic or Cubic Equation
Example To solve the following cubic equation:
x3– 2x2– x+ 2 = 0
Press 2(3) to enter the Cubic Equation Mode.
2(3)
Input each coefficient.
bw-cw
-bwcw
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Value being input into highlighted cell
Cell for input of coefficients

121
• Each time you press w, the input value is registered in the highlighted cell. Each
press of winputs values in the following sequence:
coefficient a→coefficient b→coefficient c→coefficient d
Input for coefficient dis required only for cubic equations.
• You can input fractions and value memory contents as coefficients.
After inputting the coefficients, press 1(SOLV) to solve the equations.
1(SOLV)
• Internal calculations are performed using a 15-digit mantissa, but results are dis-
played using a 10-digit mantissa and 2-digit exponent.
• An “Ma ERROR” occurs whenever the unit is unable to solve the equations.
• Pressing 1(REPT) returns to the initial display of the Cubic Equation Mode.
kk
kk
kQuadratic equations that produce multiple root (1 or 2)
solutions or imaginary number solutions
The following examples illustrate how multiple-root solutions and imaginary number
solutions are handled.
uu
uu
uTo solve a cubic equation that produces a multiple-value solution
Example To solve the following cubic equation:
x3– 4x2+ 5x– 2 = 0
bw-ewfw-cw
1(SOLV)
Quadratic and Cubic Equations 7 - 3
Highlighted solution cell value

122
uu
uu
uTo solve a cubic equation that produces an imaginary number
solution
Example To solve the following cubic equation:
x3+ x2+ x– 3 = 0
bwbwbw-dw
1(SOLV)
It may take considerable time for the calculation result of cubic equations to
appear on the display. Failure of a result to appear immediately does not mean
that the unit is not functioning properly.
kk
kk
kChanging Coefficients
You can change a coefficient either before or after you register it by pressing w.
uu
uu
uTo change a coefficient before registering it with ww
ww
w
Press the Akey to clear the current value and then input another one.
uu
uu
uTo change a coefficient after registering it with ww
ww
w
Use the cursor keys to highlight the cell that contains the coefficient that you want to
change. Next, input the value that you want to change to.
kk
kk
kClearing All the Coefficients
While in the Quadratic or Cubic Equation Mode, press the 3(CLR) function key.
This operation clears all the coefficients to zero.
3(CLR)
7 - 3 Quadratic and Cubic Equations
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7-4 What to Do When an Error Occurs
uu
uu
uError during coefficient value input
Press the Akey to clear the error and return to the value that was registered for the
coefficient before you input the value that generated the error.Try inputting a new
value again.
uu
uu
uError during calculation
Press the Akey to clear the error and display coefficient a. Try inputting values for
the coefficients again.
• Note that even when you press the Akey, the values assigned for coefficients
are retained.