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x^3-4x^2-7x+28=0

 

What are the numbers of possible number of positive real solutions?

A. Two or zero

B. Three or one

C. Two

D. One

 Jan 27, 2020
 #1
avatar+21907 
+1

x3 - 4x2 - 7x + 28  =  0

Factor x2 out of the first two terms:

x2(x - 4) - 7x + 28  =  0

Factor -7 out of the last two terms:

x2(x - 4) - 7(x - 4)  =  0

Factor x - 4 out of these two terms:

(x - 4)(x2 - 7)  =  0

Factor x2 - 7:

(x - 4)(x - sqrt(7))(x + sqrt(7))  =  0

This shows that there are 3 real answers.

 Jan 27, 2020

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