Đáp án:

Giải thích các bước giải:

`9)``169-a^2 +2ab-b^2`

`= 169- (a^2 -2ab +b^2 )`

`= 13^2 -(a-b)^2 `

`= (13-a+b)(13+a-b)`

_____________________

`10)``a^2 +6a-4b^2 +9`

`= (a^2 +6a+9)-4b^2`

`= (a+3)^2-(2b)^2`

`= (a+3-2b)(a+3+2b)`

_____________________

`11)``4x-4+9y^2 -x^2`

`= 9y^2 - (x^2 -4x+4)`

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

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

_____________________

`12)``5x^2 -10x + 5- 45t^2`

`= 5[(x^2 -2x+1)- 9t^2 ]`

`=5[(x-1)^2 -(3t)^2 ]`

`=5(x-1-3t)(x-1+3t)`

_____________________

`13)``x^2 -36y^2 t^2 -10x +25`

`= (x^2 -10x +25)-36y^2 t^2`

`= (x-5)^2 - (6yt)^2`

`= (x-5-6yt)(x-5+6yt)`

_____________________

`14)``9x^2 -16y^2 +6x+1`

`= (9x^2 +6x+1)+16y^2`

`= (3x+1)^2 -(4y)^2`

`= (3x+1-4y)(3x+1+4y)`

_____________________

`15)``x^2 -2xy+y^2 -16z^2`

`= (x-y)^2 - (4z)^2`

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

_____________________

`16)``x^2 -y^2 +14x +49`

`= (x^2 +14x +49)-y^2`

`= (x+7)^2 -y^2`

`= (x+7-y)(x+7+y)`