P(x) = -5x ³ + 8x ² – $\frac{1}{3}$ + x Q(x) = -4x + 6x ² – x ³ + 4 Tính Q(x) + P(x) Q(x) – P(x) Gấp gấp gấp 2h30 học zồi :(((

1/ $Q(x) + P(x) = ( -5x^3 + 8x^2 – \dfrac{1}{3} + x) + (-4x + 6x^2 – x^3 + 4)$

$= -5x^3 + 8x^2 – \dfrac{1}{3} + x – 4x + 6x^2 – x^3 + 4$

$= ( – 5x^3 – x^3) + (8x^2 + 6x^2) + (x-4x) – ( \dfrac{1}{3} – 4 ) $

$= -6x^3 + 14x^2 – 3x + \dfrac{11}{3}$

2/ $Q(x) – P(x) =  (-4x + 6x^2 – x^3 + 4)- ( -5x^3 + 8x^2 – \dfrac{1}{3} + x) $

$ = -4x + 6x^2 – x^3 + 4 + 5x^3 – 8x^2 + dfrac{1}{3} – x$

$ = (5x^3  – x^3) + (-8x^2 + 6x^2) + (-x-4x) – (-\dfrac{1}{3} -4)$

$ = 4x^3 – 2x^2 – 5x + \dfrac{13}{3}$