Đáp án:
a)
P(x) + Q(x) = (6x3 + 5x -3x2 – 1) + (5x2 – 4x3 – 2x + 7)
= 6x3 + 5x -3x2 – 1 + 5x2 – 4x^3 -2x + 7
=(6x3 – 4x3) + (-3x2 + 5x2) + (5x – 2x) + (-1 + 7)
= 2x3 + 2x2 + 3x + 6
b)
P(x) – Q(x) = (6x3 + 5x – 3x2 – 1) -(5x2 -4x3– 2x + 7)
= 6x3 + 5x – 3x2 – 1 -5x2 + 4x3 + 2x – 7
= (6x3 + 4x3) + (-3x2 – 5x2) + ( 5x + 2x) + (-1 -7)
= 10x3 – 8x2 + 7x – 8