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# Help! I'm confused on what to do here...

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Consider the following 2 linear equations:

$$y=-18x-11$$

$$y=-22x+15$$

Solve for the point of intersection using substitiution; thats where I'm confused.

How exactly do I solve for the point? Do I just do it like a equation with variables on both sides or something? Because if so, I'm VERY bad at that when it involves negative numbers.

Oct 13, 2018

#1
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Solving by substitution means that you solve for one variable in terms of the other from one equation,

and then substitute that into the 2nd equation to actually solve for values.

$$y = -18x - 11 \\ \text{Now we substitute this into the 2nd equation}\\ -18x-11 = -22x+15 \\ \text{Now we have an equation in one variable and we solve it as usual}\\ 4x=26 \\ x=\dfrac{26}{4} = \dfrac{13}{2}\\ y=-18\left(\dfrac {13}{2}\right) - 11 = -128$$

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Oct 13, 2018

#1
+5233
+1
$$y = -18x - 11 \\ \text{Now we substitute this into the 2nd equation}\\ -18x-11 = -22x+15 \\ \text{Now we have an equation in one variable and we solve it as usual}\\ 4x=26 \\ x=\dfrac{26}{4} = \dfrac{13}{2}\\ y=-18\left(\dfrac {13}{2}\right) - 11 = -128$$