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I need some help.

1. 2(x+y)=y+10;4(x+y)=5y+32 What's x and y?

 

2. 7(4-x)=2(y-3);4(x-y)=7-y What's x andy.

 

P.S. These are some confusing questions. : d

 Dec 21, 2018
 #1
avatar+94277 
+1

1. 2(x+y)=y+10

    4(x+y)=5y+32 

 

Simplify

 

2x + 2y  = y + 10   ⇒   2x  +  y  =  10  ⇒ y = 10 - 2x    (1)

4x + 4y = 5y + 32 ⇒    4x - y  = 32    (2)

 

Sub (1)  into (2)  for y

 

4x - (10 - 2x) = 32

6x - 10   = 32

6x = 42

x  = 7

 

And using (1)    y = 10 - 2(7)  =  -4

 

So   (x, y)  =  (7, -4)

 

 

cool cool cool

 Dec 21, 2018
 #2
avatar+94277 
+1

2.

 

7(4-x)=2(y-3)    ⇒  28 - 7x = 2y - 6 ⇒  2y + 7x  =  34    (1)

4(x-y)=7-y ⇒  4x - 4y = 7 - y  ⇒  3y - 4x = - 7      (2)

 

Multiply (1) by 3   and (2) by -2

 

6y + 21x  = 102

-6y + 8x   =   14             add these

 

29x = 116         divide both sides by 29

x = 4

 

And using  (1) to find y

2y + 7(4) = 34

2y + 28 = 34

2y = 6

y = 3

 

 

So   (x, y)  =  (4, 3)

 

 

 

cool cool cool

 Dec 21, 2018

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