\(a,x^2+6xy+9y^2=\left(x+3y\right)^2\)
b/\(\left(a-2b\right)^2=a^2-4ab+4b^2\)
c/\(\left(m+\dfrac{1}{2}\right)^2=m^2+m+\dfrac{1}{4}\)
d/\(m^2-4n^2=\left(m-2n\right)\left(m+2n\right)\)
Câu b : Ghi lại đề
Câu c :
\(\left(m+\dfrac{1}{2}\right)^2=m^2+m+\left(\dfrac{1}{4}\right)\)
Câu d :
\(m^2-4n^4=\left[m-\left(2n\right)^2\right]\left[m+\left(2n\right)^2\right]\)