K^2+2kn+n^2=? 16k^2+40kn+25n^2=?
K²+2kn+n²=(k+n)(k+n)=(k+n)² 16k²+40kn+25n²=(4k)²+2.4k.5n+(5n)²=(4k+5n)(4k+5n)=(4k+5n)²