n^4+4n是一个合数n为大于1的正整数打错了n^4+4^nsorry

Question

n^4+4n是一个合数
n为大于1的正整数
打错了
n^4+4^n
sorry

Answer 1

n^4+4^n=(n^2)^2+(2^n)^2 [据此可知,原式是正整数]=[(n^2)+(2^n)]^2-2*（n^2)*(2^n)=[(n^2)+(2^n)]^2-(n^2)*[2^(n+1)]=[(n^2)+(2^n)]^2-{n*2^[(n+1)/2]}^2={(n^2)+(2^n)+n*2^[(n+1)/2]} * {(n^2)+(2^n)-n*2^[(n+1)/...