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\(n^3+\left(n+2\right)^3=2\left(n+1\right)\left(n^2+n\left(n+2\right)+\left(n+2\right)^2\right)\)
\(\Rightarrow A=\left(n+1\right)\left(2n^2+2n\left(n+1\right)+2\left(n+2\right)^2+\left(n+1\right)^2\right)\)
Bạn tự pt tiếp nhé
\(n^7+n^2+1\)
\(=\left(n^7-n^6+n^4-n^3+n^2\right)\)\(+\left(n^6-n^5+n^3-n^2+n\right)\)
\(+\left(n^5-n^4+n^2-n+1\right)\)
\(=n^2\left(n^5-n^4+n^2-n+1\right)\)\(+n\left(n^5-n^4+n^2-n+1\right)\)
\(+\left(n^5-n^4+n^2-n+1\right)\)
\(=\left(n^2+n+1\right)\left(n^5-n^4+n^2-n+1\right)\)
Lời giải:
$N=p^{m+2}q-pq^{m+3}-p^{m+3}q^{n+4}$
$=pq(p^{m+1}-q^{m+2}-p^{m+2}q^{n+3})$
=(x-1) + xn.(x3-1)
=(x-1) + xn . (x-1)(x2+x+1)
=(x-1)[1+xn(x2+x+1)]
=(x-1)(1+xn+2+xn+1+xn)
\(p^{m+2}.q-p^{m+1}.q^3-p^2.q^{n+1}+p.q^{n+3}\)
\(=pq\left(p^{m+1}-p^mq^2-pq^n+q^{n+2}\right)\)
\(=p^m\left(p-q^2\right)-q^n\left(p-q^2\right)\)
\(=\left(p-q^2\right)\left(p^m-q^n\right)\)
..........
n3 -n2 -7n +1=n2(n-1) - 7(n-1)-6=0 <=>(n-1).(n2-7)=6