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Solve by graphing. 1. 3x+y=5 -x+2y=-4

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anya4one | Student, Undergraduate | (Level 2) Honors

Posted October 27, 2011 at 1:14 AM via web

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Solve by graphing.

1. 3x+y=5

-x+2y=-4

2 Answers | Add Yours

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hala718 | High School Teacher | (Level 1) Educator Emeritus

Posted October 27, 2011 at 1:55 AM (Answer #1)

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We have the lines:

3x+y = 5   (Line shown in black)

-x+2y = -4 ( shown in red)

We start by graphing 3x+y+5

We need to locate 2 points on the graph and then draw a line that passes through these points.

let x = 0 ==> 3x +y = 5==> 3*0 + y = 5 ==> y= 5 ==> (0,5)

Let x= 1==> 3x+5 = 5 ==> 3+y= 5==> y= 2==> (1,2)

Then we have the points (0,5) and (1,2) are on the graph of the line.

Then we will draw a line passes through these points.

Now we will graph the seond line (-x+2y)= -4

==. Let x = 0==> 2y = -4 ==> y  =-2 ==> (0,-2)

==> Let x = 2==> -2+2y = -4 ==> 2y = -2==> y= -1 (2,-1)

Then we will draw a line passes through the points (2,-1) and (0,-2)

Now we notice that the lines intersects at the point (2,-1).

Then, the solution is the point (2,-1)

 

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Wiggin42 | Student, Grade 11 | (Level 2) Valedictorian

Posted April 23, 2014 at 10:35 PM (Answer #3)

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(1) 3x+y=5

(2) -x+2y=-4

Rewrite both: 

(1) y = 5 - 3x

(2) y = (x - 4)/2

Graph: 

We can see that they intersect at point (2, -1) which is your solution. 

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