Bài 1: 

\(=3x^3y-6x^2y^2+15xy\)

Bài 2: 

\(=\left(x+y\right)^2-25=\left(x+y+5\right)\left(x+y-5\right)\)

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

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

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

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

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

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

\(=\left(x-23\right)\left(x+27\right)\)

Hok tốt

Ưm mình nhầm 

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

Hok tốt !

Bài 2: 

a: =>4x(x+5)=0

=>x=0 hoặc x=-5

b: =>(x+3)(x-3)=0

=>x=-3 hoặc x=3

1: =3(y^2+x^2+2xy-z^2)

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

2: =2(8x^3+27y^3)

=2(2x+3y)(4x^2-6xy+9y^2)

3: =(x-y)^2-25

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

Chọn B

`#040911`

`a)`

`x^2 + y^2 + 2xy - 25`

`= (x^2 + 2xy + y^2) - 25`

`= [ (x)^2 + 2*x*y + (y)^2] - 5^2`

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

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

`b)`

`x^2 + 2x - 15`

`= x^2 + 5x - 3x - 15`

`= (x^2 + 5x) - (3x + 15)`

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

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

`c)`

`x^2 - x - 2`

`= x^2 - 2x + x - 2`

`= (x^2 - 2x) + (x - 2)`

`= x(x - 2) + (x - 2)`

`= (x + 1)(x - 2)`

`d)`

`3x^2 - 11x + 6`

`= 3x^2 - 9x - 2x + 6`

`= (3x^2 - 9x) - (2x - 6)`

`= 3x(x - 3) - 2(x - 3)`

`= (3x - 2)(x - 3)`

`a, (x+y)^2-25 = (x+y+5)(x+y-5)`.

`b, x^2+2x-15 = (x+1)^2-16 = (x-3)(x+5)`.

`c, x^2-x-2=(x-2)(x+1)`

`d, 3x^2-11x+6 = (3x-2)(x-3)`.

\(a)x^2+y^2+2xy-25\\ =\left(x+y\right)^2-5^2\\ =\left(x+y+5\right)\left(x+y-5\right)\\ b)x^2+2x-15\\ =x^2+2x+1-16\\ =\left(x+1\right)^2-4^2\\ =\left(x+1+4\right)\left(x+1-4\right)\\ =\left(x+5\right)\left(x-3\right)\\ c)x^2-x-2\\ x^2+x-2x-2\\ =x\left(x+1\right)-2\left(x+1\right)\\ =\left(x+1\right)\left(x-2\right)\\ d)3x^2-11x+6\\ =3x^2-2x-9x+6\\ =x\left(3x-2\right)-3\left(3x-2\right)\\ =\left(x-3\right)\left(3x-2\right)\)

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

=x²+2xy+y²-4x²y²

=(x+y)²-4x²y²

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

2) 25-a^2+2ab-b^2

=25-(a²-2ab+b²)

=25-(a-b)²

=[5-(a-b)][5+(a-b)]

=(5-a+b)(5+a-b)

clink vào câu hỏi tương tự       

a) \(x^2-xy+x-y\)

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

\(=\left(x+1\right)\left(x-y\right)\)

b) \(x^2+5x+6\)

\(=x^2+2x+3x+6\)

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

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

\(2xy-x^2-y^2+16\)

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

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

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

= - (x² - 2xy + y² - 9) = - [ (x - y)² - 3² ] = - (x - y - 3).(x - y + 3)