Mmm thanks Heureka,
most kids here have not ever dealt with imaginary numbers so I think the question refers only to real numbers.
Lets see.
why is there no pair of linear functions that can multiply together to result f(x)= x^2+1
I am just thinking here....
Let the 2 linear functions be f(x)=ax+k and g(x)=mx+b where a,k,m, and b are all real numbers.
\((ax+k)(mx+b) = amx^2 + abx + kmx + kx\\ (ax+k)(mx+b) = amx^2 + (ab+km)x + kb\)
Now we want this to equal x^2+1
\(amx^2 + (ab+km)x + kb =x^2+1\\ \)
Equating coefficients
am=1 a=1/m
bk=1 b=1/k
ab+km=0 1/(mk) +km=0 1/(mk) = -mk
This is impossible becaus one side will be negative and the other will be positive.
Neither m nor k can be zero becasue you cannot divide by 0.
Hence 2 linear functions cannot multiply to give x^2+1
(not in the real number system anyway ) :))
While the outline of what I have done should be correct my layout is very poor.
Perhaps someone can present it better ??