Bài 4:
a: \(x^2+6x+9=\left(x+3\right)^2\)
b: \(4x^2-4x+1=\left(2x-1\right)^2\)
c: \(9x^2-12xy+4y^2=\left(3x-2y\right)^2\)
d: \(\left(x-\dfrac{y}{3}\right)\left(x+\dfrac{y}{3}\right)=x^2-\dfrac{y^2}{9}\)
e: \(x^2-10x+25=\left(x-5\right)^2\)
f: \(4-4x^2+x^4=\left(2-x^2\right)^2\)
g: \(x^2-6xy+9y^2=\left(x-3y\right)^2\)
f: \(\left(2x+y^2\right)\left(2x-y^2\right)=4x^2-y^4\)



