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x^2-4X-5=0

 Apr 3, 2017
 #1
avatar-7 
+2

Δ=16+20=36<=>Δ=6

X 1= 4 + 6 div 2=5<=> X1=5

X 2 = 4-6div 2= -1 <=> X2=-1

 Apr 3, 2017
 #2
avatar+128055 
+2

x^2 - 4x - 5  = 0        factor the trinomial

 

(x - 5) ( x + 1)  = 0

 

Set both linear factors to 0  and solve for x  

 

x - 5  = 0                         or              x + 1  = 0

add 5 to both sides                          subtract 1 from each side

x = 5                                                 x = -1

 

And those are the solutions

 

 

cool cool cool

 Apr 3, 2017

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