Math Question (1 Viewer)

[Megaton]

Actually 5i^2=-5, but (5i)^2=-25. It's a common mistake. Don't feel bad for being wrong. Feel brave for hanging yourself out there with the risk of being ridiculed. Atta kid. 

I dunno about that.  That is like saying 25^2 =50.   5i is a number.  

 

[Hooper31]

I dunno about that.  That is like saying 25^2 =50.   5i is a number.  

I do know about that. (5i)^2 and 5i^2 are not the same thing. Order of operations is big deal

(5i)^2 = 5i*5i = 5*5*i*i = 25*(-1) = -25

5i^2 = 5*i^2 = 5*(-1) = -5

Consider this: Is 7x^2 = 49x^2 ? Of course not. It's 7*x*x = 7x^2. 

 

[Megaton]

I do know about that. (5i)^2 and 5i^2 are not the same thing. Order of operations is big deal

(5i)^2 = 5i*5i = 5*5*i*i = 25*(-1) = -25

5i^2 = 5*i^2 = 5*(-1) = -5

Consider this: Is 7x^2 = 49x^2 ? Of course not. It's 7*x*x = 7x^2. 

It is not an order of operations issue.  It is nomenclature.   5i means the imaginary number 5.  There is no operation.  At least that is the convention I used decades ago.  But I am not sure there was ever a situation it mattered.  So maybe you are correct. 

 

[Hooper31]

It is not an order of operations issue.  It is nomenclature.   5i means the imaginary number 5.  There is no operation.  At least that is the convention I used decades ago.  

There's no such thing as "the imaginary number 5". There's 5 times the square root of (-1). Yes, there's an operation there. It's a multiply between the 5 and the script i. 

Since the invention of the type writer we've had to deal with attempting to communicate mathematical ideas in a single line of continuous characters. It's caused a ton of headaches for students and teachers alike. Another example is trying to use the / as a fraction bar. It creates problem in communication when ambiguity leaks in.