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Of the five quadratics listed below, four of them have two distinct roots. The fifth quadratic has a repeated root. Find the value of the repeated root.
 

-x^2 + 18x + 81

 

3x^2 - 3x - 168

 

x^2 - 4x - 4 

 

25x^2 - 30x + 9 

 

x^2 - 14x + 24 

 

this is a different question. i posted it wrong on the other one...

 Mar 19, 2020
 #1
avatar+23553 
+1

https://web2.0calc.com/questions/pls-help_106

 Mar 19, 2020
 #2
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0

Yes... but the problem was wrong... the correct problem is this one...

 Mar 19, 2020
 #3
avatar+23553 
+2

Well the method was detailed.....you should be able to do it yourself now....   cheeky

 

\(x = {-b \pm \sqrt{b^2-4ac} \over 2a}\)      this is the quadratic formula....you should know it   

 

b^2 - 4ac      is the discriminant      if  it = 0   there is one (double) root

                                                        if it = perfect square there is two roots

                                                        if it <0  there are 2 imaginary roots   

                                                        if it > 0  there are two real roots 

ElectricPavlov  Mar 19, 2020
edited by ElectricPavlov  Mar 19, 2020
 #4
avatar+111360 
+3

Look  at the fourth  one

 

The discriminant  =  (-30)^2 - 4(9)(25)  =  900 - 900  =   0

 

This  indicates a double root

 

The (double) root  is        -B / [2A]  =  - (-30) / [ 2 * 25 ]  =   30 / 50   =   3 / 5

 

 

cool cool cool

 Mar 19, 2020

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