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Find the ordered pair (s,t) that satisfies the system of equations

s/4 - 2t = 2

4t - 5s = 9

 Dec 27, 2020
 #1
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Multiply first equation by 2  to get

s/2 - 4t = 4     add to second equation to get

-4 .5 s = 13

s = - 2.89     ( or  -  26 /9)

 

Use this value of s in one of the equations to calc 't'

(-26/9)  / 4  - 2t = 2

t = -98/72   = - 49/36

 Dec 27, 2020
 #2
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+1

s/4    -2t    = 2    multiply through  by   4 ⇒   s  - 8t  = 8 ⇒  s  = 8 + 8t

Sub this into the second equation for s

 

4t  - 5(8+ 8t)    =   9   simplify

 

4t  - 40  - 40t  =  9

 

-36t =  9 + 40

 

-36t =  49

 

t = -49/36

 

And s  = 8 + 8(-49/36)    =  -26/9

 

 

cool cool cool

 Dec 27, 2020

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