<s>[INST] is $(x+1)^4-x^4$ non-prime for all natural positive integers $x$ Looking at difference between two neighbouring positive integers raised to the power 4, I found that all differences for integer neighbours up to $(999,1000)$ are non-prime.
Does this goes for all positive integers?
And can someone please prove?
 [/INST] Hint : you can write $(x+1)^4-x^4=((x+1)^2-x^2)((x+1)^2+x^2)=(x+1-x)(x+1+x)((x+1)^2+x^2)=(2x+1)((x+1)^2+x^2)$ 
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