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February 28, 2015

February 28, 2015

Posted by **Shawn** on Tuesday, August 14, 2007 at 6:54am.

Depends on the coefficients of the equation.

If in one of the equations I can solve for one of the variables without having to express it in fractions, I use substitution

3x + 7y = 9

4x + y = -3 ------> y = -4x-3, now sub that in the other equation

If not, I use elimination, that is, changing one or both of the equations to get a common coefficient for one of the variables, then subtracting or adding them to "eliminate" that variable.

2x+5y=6 ---times 3 -----> 6x+15y=18

3x-7y=1 ---times 2 -----> 6x-14y=2

now subtract them etc

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