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

a)x^2-4xy+4y^2-4

=(x²-4xy+4y²)-4

=(x-2y)²-4

=(x-2y+2)(x-2y-2)

b)16-x^2+2xy-y^2

=16-(x²-2xy+y²)

=16-(x-y)²

=[4-(x-y)][4+(x-y)]

=(4-x+y)(4+x-y)

x² - 2x + 2y - xy = (x² - 2x) - (xy - 2y) = x(x - 2) - y(x - 2) = (x - 2)(x - y)

x² + 4xy - 16 + 4y² = (x² + 4xy + 4y²) - 16 = (x + 2y)² - 16 = (x + 2y + 4)(x + 2y - 4)

cảm ơn nha

1.A

2.C

3.B

4.C

a

c

b

c

(x-1)y^2-4(x-1)y

a: \(x^2-y^2+10yz-25z^2\)

\(=x^2-\left(y^2-10yz+25z^2\right)\)

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

\(=\left(x-y+5z\right)\left(x+y-5z\right)\)

(x+y)^2 - 5y^2

x^2- 4y^2 + 4xy

= x^2 + 4xy - 4y^2

=x^2 + 2x2y - (2y)^2

= ( x - 2y )^2

 x² - 4y² + 4xy = x² + 4xy - 4y² = - (x² - 4xy + 4y²) = - ((x² - 2x.2y + (2y)²)

= - ( x - 2y)²

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

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

\(=\left[x^2-2\cdot x\cdot2y+\left(2y\right)^2\right]-25\)

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

\(=\left(x-2y-5\right)\cdot\left(x-2y+5\right)\)

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

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

\(\left(3-5x\right)^2\)

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

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

\(25x^2-30x+9=\left(5x-3\right)^2\)