Ta có :
\(m^2-4m+4=m^2-2.m.2+2^2=\left(m-2\right)^2\)
\(m^2+6mn+9n^2=m^2+2.m.3n+\left(3n\right)^2=\left(m+3n\right)^2\)
m2 - 4m + 4 = m2 - 2.2.m + 22
= ( m - 2 )2 đpcm
m2 + 6mn + 9n2 = m2 + 2.m.3n + (3n)2
= ( m + 3n )2 đpcm
Vậy ................( đề bài )