Bài 2:
a) \(4x^2-4xy+y^2=\left(2x-y\right)^2\)
b) \(25y^2-9x^2=\left(5y-3x\right)\left(5y+3x\right)\)
c) \(9x^2+6xy+y^2=\left(3x+y\right)^2\)
d) \(16x^2+40xy+25y^2=\left(4x+5y\right)^2\)
e) \(x^2-x+\dfrac{1}{4}=\left(x-\dfrac{1}{2}\right)^2\)
f) \(\dfrac{1}{4}x^2+x+1=\left(\dfrac{1}{2}x+1\right)^2\)