A)-7X2(3X - 4Y)= -7X2

Bài 1:a)-7x

²

(3x - 4y)= -7x

²

.3x + 7x

²

.4y= -21x

³

+ 28x

²

yb)(x - 3)(5x - 4)= x.5x - x.4 - 3.5x + 3.4= 5x

²

- 4x - 15x + 12= 5x

²

- 19x + 12c)(2x - 1)

²

= 4x

²

- 4x + 1d)(x + 3)(x - 3) = x

²

- 3

²

= x

²

- 9