$\text{ Thực hiện phép tính }$
$\text{ a) }$
$\text{ x(x - 2) = x² - 2x }$
$\text{ b) }$
$\text{ (x + 1)(x + 2) = }$
$\text{ x² + 2x + x + 3 = x² + 3x + 3 }$
$\text{ c) }$
$\text{ (2x³ - 6x²) : 2x = x² - 3x }$
$\text{ PTĐTTNT }$
$\text{ a) }$
$\text{ x² - 6x = x(x - 6) }$
$\text{ b) }$
$\text{ x³ - 27 = }$
$\text{ x³ - 3³ = (x - 3)(x² + 3x + 9) }$
$\text{ c) }$
$\text{ x² - y² + 4x - 4y = }$
$\text{ (x - y)(x + y) + 4(x - y) = (x + y +4)(x - y) }$
$\text{ Tìm x }$
$\text{ a) }$
$\text{ x(x - 2) - x² = 4 }$
$\text{ x² - 2x - x² = 4 }$
$\text{ -2x = 4 }$
$\text{ x = -2 }$
$\text{ b) }$
$\text{ (x + 3)² - (x - 4)(x + 8) = 1 }$
$\text{ x² + 6x + 9 - (x² + 4x - 32) = 1 }$
$\text{ x² + 6x + 9 - x² - 4x + 32) = 1 }$
$\text{ 2x + 41 = 1 }$
$\text{ 2x = -40 }$
$\text{ x = -20 }$
