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Help.

 Jan 14, 2018
 #1
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(-3i) (-4i)  =

 

-3 * - 4  * i * i   =

 

12  * i^2           ⇒ [ i^2  = -1  ]

 

12 * -1  =

 

-12

 

 

x + y  =  5   ⇒   y  =  5  - x     (1)

x^2  + y^2  =  25     (2)

 

Sub  (1)  into (2)

 

x^2  +  ( 5 - x) ^2   =  25

x^2  + x^2  - 10x  +  25  = 25   subtract 25 from both sides

2x^2  - 10x  = 0    factor

2x ( x  - 5)      set both facoters to 0 and solve for x and x  =  0   or  x  = 5

 

 

Using (1)

 

When x  = 0,     y  =  5 - 0   =  5

and

When  x  = 5,  y  = 5 - 5  =   0

 

So the solutions are    (0, 5)  and  (5, 0 )

 

 

cool cool cool

 Jan 14, 2018

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