Bài 2:
a. 9x² - 6x + 1
= (3x - 1)²
b. x²(x - 5) + 20 - 4x
= x²(x - 5) + 4(5 - x)
= x²(x - 5) - 4(x - 5)
= (x² - 4)(x - 5)
= (x - 2)(x + 2)(x - 5)
Bài 3:
a. $\frac{3x-5}{7} + \frac{4x+5}{7}$
= $\frac{3x -5+4x+5}{7}$
= $\frac{7x}{7}$
= x
b. $\frac{8x}{x^2-1} -\frac{x+2}{x-1}$ + $\frac{x-3}{x+1}$
= $\frac{8x}{(x-1)(x+1)} - \frac{(x+2)(x+1)}{(x-1)(x+1)} + \frac{(x-3)(x-1)}{(x-1)(x+1)}$
= $\frac{8x - [(x+2)(x+1)] + (x-3)(x-1)}{(x-1)(x+1)}$
= $\frac{8x - x² - 3x - 2 + x² - 2x + 3}{(x-1)(x+1)}$
= $\frac{3x+1}{(x-1)(x+1)}$
(Câu b bài 3 ko chắc lắm nhé!)
