For certain equations, the unknown can be isolated, but an answer cannot be calculated with the values stored. Then the calculator displays:
For example, if you enter an equation:
A R E A ＝ L x W
and then enter values for AREA and W, the Solver rearranges the equation to:
L ＝ A R E A ⎟ W
in order to calculate L. However, if you enter the value zero for W, the Solver cannot find an answer because division by zero is not allowed.
The Solver can isolate the unknown variable if the equation meets these conditions:
The unknown variable occurs only once in the equation.*
The only functions in which the unknown variable appears are ALOG, DATE, DDAYS (actual calendar only), EXP, EXPM1, IF (in then and else clauses only), INV, LN, LNP1, LOG, S, SQ, and SQRT.
The only operators involving the unknown variable are＋,－,x, ⎟ , and
^(power). If you are solving for a variable raised to a positive, even power (for example, A ^ 2＝4), there may be more than one solution. However, if the Solver can isolate the variable, it will find one of the solutions using the positive root. For example, the Solver rearranges A
^2 ＝4 to A＝ 4 and calculates the answer＋2.†
The unknown variable does not appear as an exponent.
*Exceptions: (1) Occurrences of the unknown variable as the argument of the S function are ignored. (2) The unknown variable can appear twice within an IF function: once in the then clause and once in the else clause.
†The Solver’s ability to find a solution iteratively can often be enhanced by rewriting the equation so that the unknown variable does not appear as a divisor. For example, the Solver may more easily solve for A if the equation 1 ÷(A ^
B:More About Calculations 241
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