SOLUTION: 2x-3y=-2 4x+y=24 This is elimination method im practicing for exam .When do we add and subtract when dealing with the elimnation method?They say when its the same you subtract

Question 593819: 2x-3y=-2
4x+y=24
This is elimination method im practicing for exam .When do we add and subtract when dealing with the elimnation method?They say when its the same you subtract and when it is different you add can someone give me and example of what this means i dont understand..
Answer by scott8148(6628) (Show Source): You can put this solution on YOUR website!
the object is to eliminate one of the variables by combining the equations

the absolute value (number) of the coefficients of the variable must be equal
___ if the coefficients have the SAME sign, then you subtract to eliminate the variable
___ if the signs are DIFFERENT, adding the equations will eliminate the variable

looking at your example; multiplying the 1st equation by 2 makes the x-coefficients in the two equations the SAME
___ subtracting the equations eliminates the x-terms and gives ___ -7y = -28

another solution; multiplying the 2nd equation by 3 makes the numbers of the y-coefficients equal with DIFFERENT signs
___ adding the equations eliminates the y-terms and gives ___ 14x = 70

sometimes, you may have to multiply both equations by different numbers to get a set of coefficients to "match up"
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