Find k

[nycmathguy]

Find k for 114. Something tells me to use the radicand of the quadratic formula. Yes?

 

[Country Boy]

Didn't you just post this?

 

[nycmathguy]

Didn't you just post this?

I posted the same attachment but not the same question. Read what I said.

 

[Country Boy]

"Find k so that x^2- kx+ 4= 0 has a repeated real solution."

A quadratic equation has a repeated solution if and only if it is of the form (x- a)^2= 0 for some a. What must "a" be for x^2- kx+ 4= 0? So what is k?

 

[nycmathguy]

"Find k so that x^2- kx+ 4= 0 has a repeated real solution."

A quadratic equation has a repeated solution if and only if it is of the form (x- a)^2= 0 for some a. What must "a" be for x^2- kx+ 4= 0? So what is k?

I think the discriminant is needed.
If b^2-4ac = 0, there will be two equal real number solutions.

Let me see.

a =1, b = -k, c = 4

b^2-4ac = (-k)^2 - 4*1*4 =k^2-16

k^2-16 = 0

(k-4)(k+4) = 0

True when k = 4 and when k = -4.
Conclusion: There are two equal real number solutions when
k = 4 and when k = -4.

 

[Country Boy]

It's not that complicated! (x- a)^2= x^2- 2ax+ a^2. Comparing that to x^2- kx+ 4, we see that a^2= 4 so a is either 2 or -2 and so k is either 4 or -4. Of course if k= -4, that would be x^2+ 4x+ 4 so they probably would not have written "-kx". I suspect k= 4 was intended.

 

[nycmathguy]

It's not that complicated! (x- a)^2= x^2- 2ax+ a^2. Comparing that to x^2- kx+ 4, we see that a^2= 4 so a is either 2 or -2 and so k is either 4 or -4. Of course if k= -4, that would be x^2+ 4x+ 4 so they probably would not have written "-kx". I suspect k= 4 was intended.

1. Try not to use words like IT'S NOT THAT COMPLICATED when helping others. This sounds very cocky.

2. I play hymns in the classical guitar style. I read and write music at an intermediate level. I also transcribe from music notation to tab and vice-versa. I would never say IT'S NOT THAT COMPLICATED. You see, it's easy for me. I am 56. I started playing guitar in 1974. I am also a former church guitarist. I say this without bragging. If you hired me as your guitar instructor, I would never say during a tutoring session: IT'S NOT THAT COMPLICATED.

3. If you are going to help me with high school probability review in just a few months from now, please show humility in your reply. Do your best to understand that not everyone has the same level of comprehension.

4. This thread is easy for you but not for me.

5. I know you from another forum. I just forgot where I saw you. Freemathhelp.com???