1)
a) 2x + 4x - 3x = 3x
b) 5x⁴·3x² = 15x⁶
c) (x - 2)² = x² - 4x + 4
d) (x - 4)(x + 4) = x² - 16
2)
a) x² - 7x = x·(x - 7)
sau x² - 7x = (x - √7x)(x + √7x)
b) x² - 64 = (x - 8)(x + 8)
c) x² + 9x + 20 = x² + 4x + 5x + 20 = x(x + 4) + 5(x + 4) = (x + 5)(x + 4)
3) x² + 6x + 9 = (x + 3)²
