# Thread: Where is the mistake

1. Now, I found this on the internet. I know there must be something wrong, but I can't find it.

2.

3. The third row does not make any sense. How can't you see it?

4. I'm sorry, I typed it wrong. Edited.

5. Still wrong, I guess it's supposed to be:

The mistake is here:

Can you find it?

6. If you square root both sides of the equation, they should stay equal, right?

7. Originally Posted by Sindrato
Now, I found this on the internet. I know there must be something wrong, but I can't find it.

for starters of what may be possibly wrong, 16-36 = 20 it is not 25 ...

16-36 = 20 - 45 = right? correct equaled/balanced equation?

i haven't done algebra in a while.

16-36 = 25-45

-20 = -20? aren't you supposed to divide something, reverse process, or balancing something?

8. It is an equation, with both sides giving -20

9. Originally Posted by Sindrato
It is an equation, with both sides giving -20
so aren't we supposed to divide -20 = -20 by 4 or something, or find the coefficient term or value to divide by doing a check balance of equation thing?...

i forgot how to do algebra... it's been years since i last had a math course.

10. I never intended to solve an equation. I just stated that this is algebraical way of getting 4=5... which is quite insane...

11. Sigh...

12. Oh gosh... I completely forgot that the expression under the square root can't be negative... thanks Twit of wit...

13. Actually, the square root of a whole positive number can be either positive or negative. The real point is there are 2 roots to every square root.

14. Originally Posted by Sindrato
I never intended to solve an equation. I just stated that this is algebraical way of getting 4=5... which is quite insane...
i'm quite lost...

all of this is to get a simplification of 5? :? is 5 the real answer, or can it be simplified even more?

15. Arcane, I don't think that was the point. You can't take the root out of negative number. (You can, but you go into imaginary numbers.) Therefore, when I tried to apply a square root on I should have gotten 20i, and not

16. Originally Posted by Arcane_Mathematician
Actually, the square root of a whole positive number can be either positive or negative. The real point is there are 2 roots to every square root.
i didn't see any square roots symbols in the equations.

surprise there aren't any Pi equations too.

17. is not negative

18. Originally Posted by FuturePasTimeCE
Originally Posted by Sindrato
Now, I found this on the internet. I know there must be something wrong, but I can't find it.

for starters of what may be possibly wrong, 16-36 = 20 it is not 25 ...

16-36 = 20 - 45 = right? correct equaled/balanced equation?

i haven't done algebra in a while.

16-36 = 25-45

-20 = -20? aren't you supposed to divide something, reverse process, or balancing something?

19. Originally Posted by Twit of wit
Sigh...

(4 - 9/2) = - (5 - 9/2)

or, - 1/2 = - 1/2

20. Originally Posted by DrRocket

I'm sorry, I made like dozen of typo's in this. Don't know why. Anyway, it was supposed to say . Edited now.

21. Twit of a Wit was on the right track here. There is a mistake the happens from when going from this first line to the second one. Both quantities, squared, are equal. Yet, their square roots have plus-or-minus possibilities.

Obviously, the plus quantities of both are not equal. However, the plus of the left side does equal the minus of the right side. Making the correct choice will yield either 4 = 4 or 5 = 5. Making the incorrect choice just shows that someone wasn't paying attention to their math and decided they were "on to something" rather than that they must have made a mistake somewhere.

Edit: I see that someone else already pointed out that you have to use the opposite signs. Sorry, I guess I just repeated and did a little more explaining.

22. Originally Posted by TheDr.Spo

Edit: I see that someone else already pointed out that you have to use the opposite signs. Sorry, I guess I just repeated and did a little more explaining.
No problem as I didn't do any explaining at all!

This was a fun one.

23. Thank you for explanation. This one left me quite confused.

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