P(x) = 4x³ – 7x² – 6x – 15 Q(x) = 8x² – 9x³ + 5x -17 a) Tính P(x) + Q(x) b) P(x) – Q(x) 30/08/2021 Bởi Eliza P(x) = 4x³ – 7x² – 6x – 15 Q(x) = 8x² – 9x³ + 5x -17 a) Tính P(x) + Q(x) b) P(x) – Q(x)
$a$) Ta có: $P(x) = 4x^3 – 7x^2 – 6x – 15$ $Q(x) = 8x^2 – 9x^3 + 5x – 17$ $⇒$ $P(x) + Q(x) = (4x^3 – 7x^2 – 6x – 15)+( 8x^2 – 9x^3 + 5x – 17)$ $= (4x^3 – 9x^3) + (-7x^2 + 8x^2) + (-6x + 5x) – (15+17)$ $= -5x^3 + x^2 – x – 32$. $b$) $P(x) – Q(x) = (4x^3 – 7x^2 – 6x – 15)-( 8x^2 – 9x^3 + 5x – 17)$ $= 4x^3 – 7x^2 – 6x – 15 – 8x^2 + 9x^3 – 5x + 17$ $= (4x^3 + 9x^3) – (7x^2 + 8x^2) – (6x+5x) – (15-17)$ $= 13x^3 – 15x^2 – 11x + 2$. Bình luận
a)P(x)+Q(x)=(4x³ – 7x² – 6x – 15)+(8x² – 9x³ + 5x -17) P(x)+Q(x)=4x³ – 7x² – 6x – 15+8x² – 9x³ + 5x -17 P(x)+Q(x)=(4x³- 9x³)+(- 7x²+8x²)+(- 6x+ 5x)+(- 15-17)-9x³ P(x)+Q(x)=-5x³+x²-x-32-9x³ b)P(x)-Q(x)=(4x³ – 7x² – 6x – 15)-(8x² – 9x³ + 5x -17) P(x)-Q(x)=4x³ – 7x² – 6x – 15-8x² + 9x³ – 5x +17 P(x)-Q(x)=(4x³+ 9x³)+(- 7x²-8x²)+(- 6x- 5x)+(- 15+17)+9x³ P(x)-Q(x)=13x³-15x²-11x+2+9x³ Bình luận
$a$) Ta có:
$P(x) = 4x^3 – 7x^2 – 6x – 15$
$Q(x) = 8x^2 – 9x^3 + 5x – 17$
$⇒$ $P(x) + Q(x) = (4x^3 – 7x^2 – 6x – 15)+( 8x^2 – 9x^3 + 5x – 17)$
$= (4x^3 – 9x^3) + (-7x^2 + 8x^2) + (-6x + 5x) – (15+17)$
$= -5x^3 + x^2 – x – 32$.
$b$) $P(x) – Q(x) = (4x^3 – 7x^2 – 6x – 15)-( 8x^2 – 9x^3 + 5x – 17)$
$= 4x^3 – 7x^2 – 6x – 15 – 8x^2 + 9x^3 – 5x + 17$
$= (4x^3 + 9x^3) – (7x^2 + 8x^2) – (6x+5x) – (15-17)$
$= 13x^3 – 15x^2 – 11x + 2$.
a)P(x)+Q(x)=(4x³ – 7x² – 6x – 15)+(8x² – 9x³ + 5x -17)
P(x)+Q(x)=4x³ – 7x² – 6x – 15+8x² – 9x³ + 5x -17
P(x)+Q(x)=(4x³- 9x³)+(- 7x²+8x²)+(- 6x+ 5x)+(- 15-17)-9x³
P(x)+Q(x)=-5x³+x²-x-32-9x³
b)P(x)-Q(x)=(4x³ – 7x² – 6x – 15)-(8x² – 9x³ + 5x -17)
P(x)-Q(x)=4x³ – 7x² – 6x – 15-8x² + 9x³ – 5x +17
P(x)-Q(x)=(4x³+ 9x³)+(- 7x²-8x²)+(- 6x- 5x)+(- 15+17)+9x³
P(x)-Q(x)=13x³-15x²-11x+2+9x³