Câu hỏi của Sakura

Question

Cho hai đa thức : A(x) = $x^5-2x^3+3x^4-9x^2+11x-6$

B(x) = $3x^4+x^5-2\left(x^3+4\right)-10x^2+9x$

Tìm C(x) biết : C(x) = A(x) - B(x)

Nguyễn Đắc Định · Accepted Answer

Ta có :

$B\left(x\right)=3x^4+x^5-2\left(x^3+4\right)-10x^2+9x$

$=x^5+3x^4-2x^3-10x^2+9x-8$

$C\left(x\right)=A\left(x\right)-B\left(x\right)$

$=x^5+3x^4-2x^3-9x^2+11x-6-\left(x^5+3x^4-2x^3-10x^2+9x-8\right)$

$=x^5+3x^4-2x^3-9x^2+11x-6-x^5-3x^4+2x^3+10x^2-9x+8$

$=x^2-2x+2$Câu trả lời: Ta có :

$B\left(x\right)=3x^4+x^5-2\left(x^3+4\right)-10x^2+9x$

$=x^5+3x^4-2x^3-10x^2+9x-8$

$C\left(x\right)=A\left(x\right)-B\left(x\right)$

$=x^5+3x^4-2x^3-9x^2+11x-6-\left(x^5+3x^4-2x^3-10x^2+9x-8\right)$

$=x^5+3x^4-2x^3-9x^2+11x-6-x^5-3x^4+2x^3+10x^2-9x+8$

$=x^2-2x+2$