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a. x^2 − 2x − 3 = 0 {nl}  b. x^2 + 2x − 3 = 0 {nl}  c. x^2 − 4x + 3 = 0 {nl}  d. x^2 + 4x + 3 = 0

 Dec 1, 2016
edited by Guest  Dec 1, 2016
edited by Guest  Dec 1, 2016
 #1
avatar+140 
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x=1 and x=-3 so it is (x-1) and (x+3)

added together -1 and 3 equal 2 and when multiplied equal -3 so look for the equation with their product (-3) as the constant (no variable) and their sum (2) as the coeficient of the middle term

so the correct answer is b.

to check

(x-1)(x+3)

x^2 + 3x - x - 3

x^2 + 2x - 3

 Dec 1, 2016
edited by Tahu8100  Dec 1, 2016
 #2
avatar+128079 
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We have the form Ax^2 + BY + C  = 0

 

In any quadratic......the sum of the solutions  =    -B/A

 

So .....   the sum of the solutions  = -2  and  note that  A  = 1   in every answer  ....so....we can solve for "B" thusly :

 

-2  = -B/A

 

-2 =  -B / 1

 

-2  = -B   →   B  = 2

 

The only equation that has B  = 2 is the second one

 

 

cool cool cool

 Dec 1, 2016

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