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Please help! Show work!! Thanks

mathelp  Apr 24, 2018
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 #1
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+3

(2x -1)*(x - 2) = 20, solve for x

 

(x - 2) (2 x - 1) = 20

 

Expand out terms of the left hand side:

2 x^2 - 5 x + 2 = 20

 

Divide both sides by 2:

x^2 - (5 x)/2 + 1 = 10

 

Subtract 1 from both sides:

x^2 - (5 x)/2 = 9

 

Add 25/16 to both sides:

x^2 - (5 x)/2 + 25/16 = 169/16

 

Write the left hand side as a square:

(x - 5/4)^2 = 169/16

 

Take the square root of both sides:

x - 5/4 = 13/4 or x - 5/4 = -13/4

 

Add 5/4 to both sides:

x = 9/2 or x - 5/4 = -13/4

 

Add 5/4 to both sides:

 

x = 9/2 * 2 - 1 = 8 units.                                                           or x = -2(Discard this one)

Guest Apr 24, 2018
 #2
avatar+86613 
+3

We have

 

Area  = L * W    

 

20 = (2x - 1) (x - 2)   simplify

 

20  = 2x^2 - x - 4x + 2     subtract 20 from both sides and we have

 

2x^2 - 5x - 18  = 0      factor

 

(2x - 9) ( x + 2)  =   0

 

Only  the first factor set to 0  will yield a positive result for x

 

2x  - 9  =  0

2x  = 9

x = 9/2 

 

So....the length  is  2(9/2) - 1   =    9 -  1   =   8

 

 

cool cool cool

CPhill  Apr 24, 2018

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