Question 775297
SUBSTITUTE the number for x, no matter only real or complex.  DO THE ARITHMETIC according to the function's definition.  SIMPLIFY into the final result.  


Are you yet unstudied about imaginary numbers, and the imaginary number unit, i ?

To be simple, the way this unit works is {{{i*i=i^2=-1}}}.  
As used in complex numbers, {{{(a+bi)+(c+di)=a+c + (b+d)i}}};
and {{{(a+bi)(c+di)=ac+bci+adi+bdi^2=ac+bdi^2+bci+adi=ac+(-1)bd+(bc+ad)i=ac-bd+(bc+ad)i}}}.
The only new idea here is {{{i^2=-1}}}.  


Have no fear about this.  Just try working through.





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Your question description has been adjusted a little for better rendering of notation.