Solving equations with radical sign

[AbsentMinded]

Aha, I see! Thank you so much! It was an equation, and I had to simplify it. I've got it all down now.

There is just one more radical equation I have to solve.

4 = sqrt x^2 - 6x

Or:



I don't really know how to begin with this one.

Thanks for all your help, it is very much appreciated! (If I should put this in a new thread, instead, please let me know.)

(BTW, I don't know why it put "equation" as a link, I just typed the word normally.)

 

[AbsentMinded]

Ok, I see what you're saying. And I'll keep all that in mind, thank you.

Let me try to finish it.

(x + 2)(x - 8) = 0

x = -2 or 8.

-2 doesn't work.

X = 8.

 

[Deleted member 4993]

Ok, I see what you're saying. And I'll keep all that in mind, thank you.

Let me try to finish it.

(x + 2)(x - 8) = 0

x = -2 or 8.

-2 doesn't work.

X = 8.

Correct - good work.

It will be useful to show that x = 8 DOES work.

check:

\(\displaystyle \sqrt{x^2 - 6*x} \ = \ \sqrt{8^2 - 6*8} \ = \ \sqrt{16} \ = \ 4 \)

 

[Deleted member 4993]

EEKs ... ... I have to go to the corner now....

Mathematically x = -2 is a valid answer - but there might be physical restrictions (like x = no. of bananas), that can restrict the answer.

Upshot of it is that you need to check for mathematical validity and physical validity (for a physics problem).