Question

cm n⁴-n²=n²(n+1)(n-1)

Answer 1

Ta có: 

\(\left(n+1\right)\left(n-1\right)=\left(n+1\right)n-\left(n+1\right)=n^2+n-n-1=n^2-1\)

\(\Rightarrow n^2\left(n+1\right)\left(n-1\right)=n^2\left(n^2-1\right)=n^4-n^2\)

Vậy \(n^4-n^2=n^2\left(n+1\right)\left(n-1\right)\)

Answer 2

Bài mk cũng gần giống Dung:

VP=(n+1)(n-1)=n.(n-1)+1(n-1)=n^2-n+n-1=n^2+0-1=n^2-1

Khi đó n^2.(n+1(n-1)=n^2.(n^2-1)=n^4-n^2=VT

=>VT=VP (đpcm)

Answer 3

Answer 4

 Nguyễn thị thu hà nói j zậy