Giải thích các bước giải:
a/. a² - 4b²
= a² - (2b)²
= (a - 2b)(a + 2b)
b/. 25a² - 1
= (5a)² - 1²
= (5a - 1)(5a + 1)
c/. a² - 9
= a² - 3²
=(a - 3)(a + 3)
d/. `1/4`a² - `9/(25)`
= (`1/2`a)² - (`3/5`)²
= (`1/2`a - `3/5`)(`1/2`a + `3/5`)
e/. `9/4`a4 - `(16)/(25)`
= (`3/2`a²)² - (`4/5`)²
= (`3/2`a² - `4/5`)(`3/2`a² + `4/5`)
f/. (2a + b)² - a²
= (2a - a+ b)(2a + a + b)
= (2a + b - a)(2a + b + a)
= (a + b)(3a + b)
g/. 16(x - 1)² - 25(x + y)²
= [4(x - 1)]² - [5(x + y)]²
= [4(x - 1) - 5(x + y)] [4(x - 1) + 5(x + y)]
= (4x - 4 - 5x - 5y)(4x - 4 + 5x + y)
= (4x - 5x - 5y- 4 )(4x + 5x + y - 4)
= (-x - 5y - 4)(9x + y - 4)
