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y=-3x-13

9x-2y=27

 Jan 3, 2017

Best Answer 

 #2
avatar+128406 
+5

Very well explained, Ninja....!!!!

 

 

 

cool cool cool

 Jan 3, 2017
 #1
avatar+355 
+5

Substitution:

 

Change second equation to point slope:

y=-3x-13

9x-2y=27<---Second Eq.

 

2y = 9x - 27

 

y = (9x - 27)/2

y=-3x - 13

 

Since they both equal y, you can set them equal to each other.

 

(9x - 27)/2 = -3x - 13 -------------Multiply both sides by 2

 

9x - 27 = -6x - 26

 

15x = 1

 

x = 1/15

 

Now plug this into either of the equations to get y. I will do the first one

 

y = -3x - 13 ---------Plug in 1/15 for x

 

y = -3/15 -13

 

y = -1/5 - 13

 

y = -13 1/5

 

y = -66/5 OR -13.2

 

x = 1/15 OR 0.06666666666666666666666666666666666666666666666666666667

 

Elimination Method-->

 

Set first equation to standard form. 

 

y = -3x - 13<--------First Equation

9x - 2y = 27

 

y = -3x - 13

 

y + 3x = -13<-------------Standard form

-2y + 9x = 27<------------Flipped x and y on the left side. Doesn't change the original equation

 

Now multiply the top equation by 2

 

2(y + 3x) = 2 * -13

 

2y + 6x = -26

-2y + 9x = 27

 

Now add both equations. This eliminates y so now you can solve for x.

 

2y + 6x -2y + 9x = -26 + 27

 

15x = 1

 

x = 1/15

 

Now you just do the stuff we did for substitution and solve for y.

 

y = -3x - 13 ---------Plug in 1/15 for x

 

y = -3/15 -13

 

y = -1/5 - 13

 

y = -13 1/5

 

y = -66/5 OR -13.2<-----------------------------------------------------------------------------------------Answer for y

 

x = 1/15 OR 0.06666666666666666666666666666666666666666666666666666667<-----Answer for x

 Jan 3, 2017
 #2
avatar+128406 
+5
Best Answer

Very well explained, Ninja....!!!!

 

 

 

cool cool cool

CPhill Jan 3, 2017
 #3
avatar+355 
+5

Thanks CPhill!!! Tiring.....!!!

NinjaAnswer  Jan 3, 2017

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