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Excel's Formula - sisman

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424<br />

Part V: Miscellaneous <strong>Formula</strong> Techniques<br />

Figure 16-6: This workbook uses circular references to calculate several recursive equations.<br />

Solving simultaneous equations using a circular reference<br />

In some cases, you can use circular references to solve simultaneous equations. Consider the two<br />

simultaneous equations listed here:<br />

3x + 4y = 8<br />

3x + 8y = 20<br />

You need to find the value of x and the value of y that satisfies both equations. First, rewrite the<br />

equations to express them in terms of x and y. The following represents the first equation,<br />

expressed in terms of x:<br />

x = (8 – 4y)/3<br />

The following equation represents the second equation, expressed in terms of y:<br />

y = (20 – 3x)/8<br />

As shown in Figure 16-7, cell B5 is named X, and cell B6 is named Y. The formulas in these cells<br />

mirror the previous equations. The formula in B5 (X) is<br />

=(8–(4*Y))/3<br />

The formula is cell B6 (Y) is<br />

=(20–(3*X))/8<br />

The figure also shows a chart that plots the two equations. The intersection of the two lines represents<br />

the values of X and Y that solve the equations.

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