a) V = x(x + 1)(x - 1) = x(x^2 - 1) = x^3 - x b) Thay x = 4 vào V = x^3 - x, ta có: V = 4^3 - 4 = 64 - 4 = 60.

2x^4 - 3x^3 - 3x^2 + 6x - 2 = (x^2 - 2)(2x^2 - 3x + 1)

5x(4x^2 - 2x + 1) - 2x(10x^2 - 5x + 2) = -36

20x^3 - 10x^2 + 5x - 20x^3 + 10x^2 - 4x = -36

(20x^3 - 20x^3) + (-10x^2 + 10x^2) + (5x - 4x) = -36

0 + 0 + x = -36

x = -36

Vậy x = -36.

a) Tìm tổng P(x) + Q(x)

P(x) + Q(x) = (x^4 - 5x^3 + 4x - 5) + (-x^4 + 3x^2 + 2x + 1)

= x^4 - 5x^3 + 4x - 5 - x^4 + 3x^2 + 2x + 1

= (x^4 - x^4) - 5x^3 + 3x^2 + (4x + 2x) + (-5 + 1)

= -5x^3 + 3x^2 + 6x - 4

Vậy P(x) + Q(x) = -5x^3 + 3x^2 + 6x - 4

b) Tìm đa thức R(x)

Ta có: P(x) = R(x) + Q(x) Suy ra: R(x) = P(x) - Q(x)

R(x) = (x^4 - 5x^3 + 4x - 5) - (-x^4 + 3x^2 + 2x + 1)

= x^4 - 5x^3 + 4x - 5 + x^4 - 3x^2 - 2x - 1

= (x^4 + x^4) - 5x^3 - 3x^2 + (4x - 2x) + (-5 - 1)

= 2x^4 - 5x^3 - 3x^2 + 2x - 6

Vậy R(x) = 2x^4 - 5x^3 - 3x^2 + 2x - 6