2. Solving Systems of Linear Equations by Substitution
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Which of the variables has the lowest coefficient next to it?
Equation to Be Manipulated: 5x-y=5
Variable to Be Isolated: y
Which variable in which equation would be the easiest to isolate? Well, the coefficient of y in the second equation is - 1, which makes it easy to isolate y. 5x+3y=11 & (I) 5x-5=y & (II) If we rearrange the second equation, we get the following system. 5x+3y=11 & (I) y= 5x-5 & (II) We could have chosen to isolate y in the first equation. However, in the first equation, the coefficient of y is 3 and the constant is 11. The fact that we have easier, smaller numbers in the second equation makes this the best candidate.