Posted by **Amanda** on Monday, February 18, 2008 at 9:52pm.

1. Explain the advantages and disadvantages of both the substitution method and the elimination method for solving a system.

Help please. The only reasons I can think of is because in substitution it might be more difficult cause there's a possibility of working with fractions.

- Math -
**Reiny**, Monday, February 18, 2008 at 10:03pm
Actually, that is the best reason.

I use the following criterium.

If I see one of the variables having a coefficient of 1 OR -1, I solve for that variable and use substitution, resulting in no fractions, unless the equation contains fractions to begin with.

As a matter of fact if I see fractions in either one of my equations, I usually multiply each term by the LCD of the fractions, thereby eliminating the fractions.

g. 4x+5y = 12

3x-y = 9

I would solve for y in the second, then sub that into the first.

Of course if the answer itself is a fraction you would be stuck with thAT.

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