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Helen [10]
4 years ago
9

5x + 6y = 18 and 18x -15y =36

Mathematics
2 answers:
stira [4]4 years ago
4 0
5x+6y=18

5x=18-6y

x=(18-6y)/5

Use that in the other equation
18(18-6y)/5 - 15y = 36

64.8-21.6y - 15y = 36

28.8=36.6y
.7868=y

Now put that number in for y on the first equation

5x+6(.78) = 18
5x + 4.68 = 18
5x = 13.32
x = 2.66
and y = .78


Bond [772]4 years ago
3 0
Solution :<span><span> {x,y,z} = {-3,-2,-1}</span>  </span>System of Linear Equations entered :<span><span>  [1] x + 6y + 3z = -18 </span><span>  [2] -x + 6y - 3z = -6 </span><span>  [3] 5x - 6y + 3z = -6 </span></span>Solve by Substitution :

// Solve equation [1] for the variable  x  
 

<span> [1] x = -6y - 3z - 18 </span>

// Plug this in for variable  x  in equation [2]

<span><span>  [2] -(-6y-3z-18) + 6y - 3z = -6 </span><span>  [2] 12y = -24 </span></span>

// Plug this in for variable  x  in equation [3]

<span><span>  [3] 5•(-6y-3z-18) - 6y + 3z = -6 </span><span>  [3] - 36y - 12z = 84 </span></span>

// Solve equation [2] for the variable  y  

<span><span>  [2] 12y = - 24</span>  <span>  [2] y = - 2</span> </span>

// Plug this in for variable  y  in equation [3]

<span><span>  [3] - 36•(-2) - 12z = 84 </span><span>  [3] - 12z = 12 </span></span>

// Solve equation [3] for the variable  z  

<span><span>  [3] 12z = - 12</span>  <span>  [3] z = - 1</span> </span>

// By now we know this much :

<span><span>  x = -6y-3z-18</span> <span>  y = -2</span> <span>  z = -1</span></span>

<span>// Use the  y  and  z  values to solve for  x  
</span><span><span>  x = </span>-6(-2)-3(-1)-18 = -3 </span>

Solution :<span><span> {x,y,z} = {-3,-2,-1}</span>  Processing ends successfully </span>
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