a)  \(\frac{1}{9}x^4-2x^2y+9y^2=\left(\frac{1}{3}\right)^2\left(x^2\right)^2-2x^2y+\left(3y\right)^2\)

\(=\left(\frac{1}{3}x^2\right)^2-2\frac{1}{3}x^23y+\left(3y\right)^2\)

\(=\left(\frac{1}{3}x^2-3y\right)^2\)

b)  \(25x^2-20xy+4y^2=\left(5x\right)^2-2.5x.2y+\left(2y\right)^2\)

\(=\left(5x-2y\right)^2\)

\(\frac{1}{9}x^4-2x^2y+9y^2\)

\(=\left(\frac{1}{3}x^2\right)^2-2\times\frac{1}{3}x^2\times3y+\left(3y\right)^2\)

\(=\left(\frac{1}{3}x^2-3y\right)^2\)

\(25x^2-20xy+4y^2\)

\(=\left(5x\right)^2-2\times5x\times2y+\left(2y\right)^2\)

\(=\left(5x-2y\right)^2\)

a) \(x^2+x+\frac{1}{4}=\left(x+\frac{1}{2}\right)^2\)

b) \(x^2+12xy+36y^2=\left(x+6y\right)^2\)

c) \(4x^2-12xy+9y^2=\left(2x-3y\right)^2\)

d) Không phải hằng đẳng thức \(\left(x^2-2x+4=\left(x-1\right)^2+3\right)\)

e) \(25x^2+4y^2-20xy=\left(5x-2y\right)^2\)

\(a.x^2+x+\frac{1}{4}=x^2+2.x.\frac{1}{4}+\left(\frac{1}{4}\right)^2\)

                        \(=\left(x+\frac{1}{4}\right)^2\)

b)  \(x^2+12xy+36xy^2=x^2+2.x.y+y^2\)

\(a.x^2+x+\frac{1}{4}=x^2+2.x.\frac{1}{4}+\left(\frac{1}{4}\right)^2\)

                        \(=\left(x+\frac{1}{4}\right)^2\)

b)  \(x^2+12xy+36xy^2=x^2+2.x.y+y^2\)

\(a.x^2+x+\frac{1}{4}=x^2+2.x.\frac{1}{4}+\left(\frac{1}{4}\right)^2\)

                        \(=\left(x+\frac{1}{4}\right)^2\)

b)  \(x^2+12xy+36xy^2=x^2+2.x.y+y^2\)

\(a.x^2+x+\frac{1}{4}=x^2+2.x.\frac{1}{4}+\left(\frac{1}{4}\right)^2\)

                        \(=\left(x+\frac{1}{4}\right)^2\)

b)  \(x^2+12xy+36xy^2=x^2+2.x.y+y^2\)

d) \(x^2-2x+4=x^2-2.x.4+4^2\)

                          \(=\left(x-4\right)^2\)

e) \(25x^2+4y^2-20xy=\left(5x\right)^2-2.5x.2y+\left(2y\right)^2\)

                                      \(=\left(5x-2y\right)^2\)

 ^...^ ^_^ Bài làm có gì ko hiểu bạn cứ hỏi nhé ^_^

a) x² + x + \(\frac{1}{4}\) = ( x + \(\frac{1}{2}\) )²

b) x² + 12xy + 36xy² = ( x + y)²

c) 4x² - 12xy + 9y² = ( 2x - 3y)²

d) x² - 2x + 4 = ( x - 2)²

e) 25x² + 4y² - 20xy = ( 5x - 2y)²

a. x² + 6x + 9 = (x + 3)²

b. 25 + 10x + x² = (5 + x)²

c. x² + 8x + 16 = (x + 4)²

d. x² + 14x + 49 = (x + 7)²

e. 4x² + 12x + 9 = (2x + 3)²

f. 9x² + 12x + 4 = (3x + 2)²

h. 16x² + 8 + 1 = (4x + 1)²

i. 4x² + 12xy + 9y² = (2x + 3y)²

k. 25x² + 20xy + 4y² = (5x + 2y)²

a) \(=\left(x+3\right)^2\)

b) \(=\left(x+5\right)^2\)

c) \(=\left(x+4\right)^2\)

d) \(=\left(x+7\right)^2\)

e) \(=\left(2x+3\right)^2\)

f) \(=\left(3x+2\right)^2\)

h) \(=\left(4x+1\right)^2\)

i) \(=\left(2x+3y\right)^2\)

k) \(=\left(5x+2y\right)^2\)

a) \(25x^2-20xy+4y^2\)

\(=\left(5x\right)^2-2.5x.2y+\left(2y\right)^2\)

\(=\left(5x-2y\right)^2\)

b) \(4x^2+9+12x\)

\(=\left(2x\right)^2+3^2+2.2x.3\)

\(=\left(2x+3\right)^2\)

c) \(\frac{1}{4}+3x+9x^2\)

\(=\left(\frac{1}{2}\right)^2+2.\frac{1}{2}.3x+\left(3x\right)^2\)

\(=\left(\frac{1}{2}+3x\right)^2\)

d) \(-6xy+x^2+9y^2\)

\(=x^2-6xy+9y^2\)

\(=x^2-2.x.3y+\left(3y\right)^2\)

\(=\left(x-3y\right)^2\)

Nguyễn Bích Quỳnh: bạn chúc như một vị thần

a             \(x^2-6x+9=x^2-2.3.x+3^2=\left(x-3\right)^2\)

b             \(4y^2+y+\frac{1}{16}=\left(2y\right)^2+2.2y.\frac{1}{4}+\left(\frac{1}{4}\right)^2=\left(2y+\frac{1}{4}\right)^2\)

a, \(25x^2+5xy+\frac{1}{4}y^2=\left(5x\right)^2+2.5x.\frac{1}{2}y+\left(\frac{1}{2}y\right)^2\)

\(=\left(5x+\frac{1}{2}y\right)^2\)

b, \(9x^2+12x+4=\left(3x\right)^2+2.3x.2+2^2=\left(3x+2\right)^2\)

c, \(x^2-6x+5-y^2-4y=\left(x^2-6x+9\right)-\left(y^2+4y+4\right)\)

\(=\left(x-3\right)^2-\left(y+2\right)^2=\left(x-y-5\right)\left(x+y-1\right)\)

d, \(\left(2x-y\right)^2+4\left(x+y\right)^2-4\left(2x-y\right)\left(x+y\right)\)

\(=\left(2x-y\right)^2-2\left(2x-y\right)\left(2x+2y\right)+\left(2x+2y\right)^2\)

\(=\left(2x-y+2x+2y\right)^2=\left(4x+y\right)^2\)

Có cái cc

a,9a²-30a+25

=(3a)²-30a+5²

=(3a-5)²

b,1+4x+4x²

=4x²+4x+1

=(2x)²+4x+1²

=(2x+1)²

c,a²+16+8a

=a²+8a+16

=a²+8a+4²

=(a+2)²

d,25x²+4y²-20xy

=25x²-20xy+4y²

=(5x)²-20xy+(2y)²

=(5x-2y)²