Giải thích các bước giải:
a/. (x - 4)(x + 4)(x + 2)
= (x² + 4x - 4x - 16)(x + 2)
= (x² - 16)(x + 2)
= x³ + 2x² - 16x - 32
b/. (15x - 3y)(x³ - x²y + 4)
= 15x4 - 15x³y + 60x - 3x³y + 3x²y² - 12y
= 15x4 - (15x³y + 3x³y) + 3x²y² + 60x - 12y
= 15x4 - 18x³y + 3x²y² + 60x - 12y
c/. 18x³y²(3x + y²)(3x² - y)
= (54x4y² + 18x³y4)(3x² - y)
= 162x6y² + 54x4y³ + 54x5y4 - 18x³y5
d/. (`1/3`x - 1)(3x - 2)
= `1/3`x. 3x - `1/3`x . 2 - 1 .3x + 1. 2
= x² - `2/3`x - 3x + 2
= x² - (`2/3`x + 3x) + 2
= x² - `(11)/3`x + 2
e/. (2x - 17)(x - 5)
= 2x² - 10x - 17x + 85
= 2x² - (10x + 17x) + 85
= 2x² - 27x + 85
f/. (x - `1/4`)(x + `1/4`)(16x - 1)
= [(x² + `1/4`x - `1/4`x - `1/(16)`](16x - 1)
= (x² - `1/(16)`)(16x - 1)
= 16x³ - x² - `1/(16)`.16x + `1/(16)`
= 16x³ - x² - x + `1/(16)`
