Why Does the Negative Sign Appear in Second Differentiation of Exponentials?

[lioric]

Plz give me an easy explanation

I do know about the differentiation and second differentiation. I just don't get how that negetive sign comes in front of the exponent in the second differentiation

 

[jedishrfu]

The "j" represent the imaginary number square-root of minus one. Modern math representations more commonly use "i". However electrical engineering texts will use "j" so as not to confuse the issue of current represented as "i".

https://en.wikipedia.org/wiki/Imaginary_number

Consequently you get the -1 in the second derivative as j*j = -1

https://en.wikipedia.org/wiki/Imaginary_unit

 

[lioric]

Thank you very much