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- In Best Answer‚Ñ¢, the OBJECTIVE cell and all CONSTRAINT Cells
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- must contain "linear" formulas. This means that only the following
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- operators may be used:
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-
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- + - * / SUM()
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- From an algebraic perspective, a linear function may always be
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- expressed as:
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-
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- aX + bY + cZ + ... + d
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-
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- where X, Y, and Z are adjustable cells, and a, b, c, and d are
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- constants.
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- This means that:
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-
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- 1) ADJUSTABLES may not be multiplied by one another
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- or by themselves.
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- 2) No ADJUSTABLE may appear in the divisor of an expression,
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- directly or indirectly (through another cell).
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- It is often possible to restructure non-linear CONSTRAINTS to
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- make them linear. For example, suppose you wished to constrain
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- B3 to be no more than 40% of (B3 + B4), where B3 and B4 are
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- both ADJUSTABLE cells. The obvious way to express this
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- CONSTRAINT is:
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-
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- =0.4 - B2/(B2+B3)
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-
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- but this expression is non-linear. This constraint may be
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- changed, through simple algebraic rules, to a different form:
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- = 0.4*B3 - 0.6*B2
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-
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- which is a legal, linear constraint.
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-