why is there no pair of linear functions that can multiply together to result f(x)= x^2+1
why is there no pair of linear functions that can multiply together to result f(x)= x^2+1
There is a pair of linear functions:
\(\begin{array}{rcll} x^2+1 &=& (x-i)\cdot (x+i) \qquad & | \qquad i \text{ is the imaginary number} \end{array}\)
\(\begin{array}{rcll} x^2+1 &=& (x-i)\cdot (x+i) \\ &=& x^2 - i^2 \qquad & | \qquad i^2 = -1 \\ &=& x^2 - (-1) \\ &=& x^2 +1 \end{array}\)
why is there no pair of linear functions that can multiply together to result f(x)= x^2+1
There is a pair of linear functions:
\(\begin{array}{rcll} x^2+1 &=& (x-i)\cdot (x+i) \qquad & | \qquad i \text{ is the imaginary number} \end{array}\)
\(\begin{array}{rcll} x^2+1 &=& (x-i)\cdot (x+i) \\ &=& x^2 - i^2 \qquad & | \qquad i^2 = -1 \\ &=& x^2 - (-1) \\ &=& x^2 +1 \end{array}\)
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 ??
Let's suppose that there could be.....call the functions
f(x) = ax + b and g(x) = cx + d
So ...... a and c must be reciprocals and so must b and d....so we have
(ax + b) ((1/a)x + (1/b) =
x^2 + (b/a)x + (a/b)x + 1
And this = x^2 + 1
Which implies that
[ (b/a) + (a/b)] = 0
Which implies that
[b^2 + a^2] / ab = 0
Which implies that
b^2 + a^2 = 0
But this is only possible if a and b = 0
But....if a and b = 0
Then f(x) = 0x + 0 = 0
And g(x) = (1/0)x + (1/0)
Thus : f(x) * g(x) = 0 times an undefined expression ....which could never be any function!!!