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Solving Equations

7–1

File name 33s-English-Manual-040130-Publication(Edition 2).doc Page : 388

Printed Date : 2004/1/30 Size : 13.7 x 21.2 cm

Solving Equations

In chapter 6 you saw how you can use

to find the value of the left–hand

variable in an

assignment–type equation. Well, you can use SOLVE to find the

value of

any variable in any type of equation.

For example, consider the equation

– 3y = 10

If you know the value of

y in this equation, then SOLVE can solve for the unknown

x. If you know the value of x, then SOLVE can solve for the unknown y. This works

for "word problems" just as well:

Markup

Cost = Price

If you know any two of these variables, then SOLVE can calculate the value of the

third.

When the equation has only one variable, or when known values are supplied for

all variables except one, then to solve for

x is to find a root of the equation. A root

of an equation occurs where an

equality or assignment equation balances exactly,

or where an

expression equation equals zero. (This is equivalent to the value of the

equation being zero.)

Solving an Equation

To solve an equation for an unknown variable:

Press

and display the desired equation. If necessary, type the

equation as explained in chapter 6 under "Entering Equations into the

Equation List."

2. Press

then press the key for the unknown variable. For example, press

X to solve for x. The equation then prompts for a value for every other

variable in the equation.

3. For each prompt, enter the desired value:

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