=4x^2+2xy-18xy-9y^2

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

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

4x^2+2xy-18xy-9y^2

=2x(2x+y)-9y(2x+y)

=(2x-9y)(2x+y)

Sorry bài trên mình làm sai 

\(xy^3-5x^2\)

\(=x\cdot y^3-x\cdot5x\)

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

\(y^2+3y\)

\(=y\cdot y+y\cdot3\)

\(=y\left(y+3\right)\)

1. 5x² - 4x

= x(5x - 4)

2. 8x²(x - 3y) - 12x(x - 3y)

= (8x² - 12x)(x - 3y)

= 4x(2x - 3)(x - 3y)

3. 3(x - y) - 5x(y - x)

= 3(x - y) + 5x(x - y)

= (3 + 5x)(x - y)

\(x^3-10x^2+25x-16xy^2\)

\(=x\left(x^2-10x+25-16y^2\right)\)

\(=x\left[\left(x-5\right)^2-16y^2\right]\)

\(=x\left(x-4y-5\right)\left(x+4y-5\right)\)

p/s: chúc bạn học tốt

\(=\left(x^2+y^2-5\right)^2-4\left(xy-2\right)^2=\left(x^2+y^2-5+2xy-4\right)\left(x^2+y^2-5-2xy+4\right)\)
\(=\left(\left(x+y\right)^2-9\right)\left(\left(x-y\right)^2-1\right)=\left(x+y-3\right)\left(x+y+3\right)\left(x-y+1\right)\left(x-y-1\right)\)

(x^2+y^2-5)^2 - 4x^2y^2 - 16xy -16
= (x^2 + y^2 - 5)^2 - (4x^2y^2 + 16xy + 16)
= (x^2 + y^2 - 5)^2 - (2xy + 4)^2
= (x^2 + y^2 - 5 - 2xy - 4)(x^2 + y^2 - 5 + 2xy + 4)
= [(x - y)^2 - 9][(x + y)^2 - 1]
=(x-y-3)(x-y+3)(x+y-1)(x+y+1)

Đề sai rồi bạn

a, \(100a^2-\left(a^2+25\right)^2=\left(10a\right)^2-\left(a^2+25\right)^2\)

\(=\left(10a-a^2-25\right)\left(10a+a^2+25\right)=-\left(a-5\right)^2\left(a+5\right)^2\)

b,\(-5\left(xy\right)^3-5\left(xy\right)^3=-10\left(xy\right)^3\)

c,\(16+2\left(xy\right)^3=2\left(2+xy\right)\left(4-2xy+x^2y^2\right)\)

a: =x(x-5)

a) \(=x\left(x-5\right)\)

b) \(=\left(x+3y-3y\right)\left(x+3y+3y\right)=x\left(x+6y\right)\)

c) \(=x\left(x+y\right)-3\left(x+y\right)=\left(x+y\right)\left(x-3\right)\)

b,=(x+3y-3y(x+3y+3y)

= x(x+6y)

** Sửa: $125x^3-5x-3y+27y^3$
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Lời giải:

$125x^3-5x-3y+27y^3=(125x^3+27y^3)-(5x+3y)$

$=[(5x)^3+(3y)^3]-(5x+3y)$

$=(5x+3y)(25x^2-15xy+9y^2)-(5x+3y)$

$=(5x+3y)(25x^2-15xy+9y^2-1)$

Đề sai rồi bạn