Giải thích các bước giải:
a, (5x - 4)² - 9x²
⇔ (5x - 4)² - (3x)²
⇔ (5x - 4 - 3x) (5x - 4 + 3x)
⇔ (2x - 4)(8x - 4)
⇔ 2(x - 2). 4.(2x -1)
⇔ 8(x - 2)(2x -1)
b, (2x - 3)² - (x + 1)²
⇔ [(2x - 3) - (x + 1)](2x - 3 + x + 1)
⇔( 2x - 3 - x - 1)(3x - 2)
⇔ (x - 4)(3x - 2)
c, (5x - 2)² - (3x + y) ²
⇔ [(5x - 2) - (3x + y)](5x - 2 + 3x + y)
⇔ ( 5x - 2 - 3x - y)(8x + y - 2)
⇔ (2x - y - 2)(8x + y - 2)