Đáp án+Giải thích các bước giải:

`color{#0A1433}{#}color{#142966}{ha}color{#1F3D99}{phu}color{#2E5CE6}{ongv}color{#5C85FF}{y0}color{#85A3FF}{1}color{#ADC2FF}{1}color{#C2D1FF}{2}`

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

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

`7, x^2 - y^2 - 6y - 9 = x^2 -(y+3)^2 = (x-y-3)(x+y+3)`

`10, 4x^2 - y^2 + 4x + 1 = (2x+1)^2 - y^2 = (2x+1 - y)(2x+1+y)`

`13, y^2 - x^2 - 12y + 36 = (y-6)^2 - x^2 = (y-6-x)(y-6+x)`

`16, 1-8x + 16x^2 - y^2 = (1-4x)^2 - y^2 = (1-4x-y)(1-4x+y)`

`19, y^2 - 14y - 25x^2 + 49 = (y-7)^2 - 25x^2 = (y-7-5x)(y-7+5x)`