Question

Cho em hỏi:

A(x) = 6x³ - x - 1

B(x) = 5x³ - 2x + x² - 1

a) Tính: P(x) = A(x) + B(x).

b) Tính: Q(x) = A(x) - B(x).

c) Tính U(x) biết 2U(x) + 3A(x) = B(x).

Nhiêu đó thôi ạ!

Answer 1

a: \(P\left(x\right)=6x^3-x-1+5x^3+x^2-2x-1=11x^3+x^2-3x-2\)

b: \(Q\left(x\right)=6x^3-x-1-5x^3-x^2+2x+1=x^3-x^2+x\)

c: \(2\cdot U\left(x\right)=5x^3-2x+x^2-1-3\cdot\left(6x^3-x-1\right)\)

\(\Leftrightarrow2\cdot U\left(x\right)=5x^3+x^2-2x-1-18x^3+3x+3\)

\(\Leftrightarrow2\cdot U\left(x\right)=-13x^3+x^2+x+2\)

hay \(U\left(x\right)=-\dfrac{13}{2}x^3+\dfrac{1}{2}x^2+\dfrac{1}{2}x+1\)

Answer 2

\(a,P\left(x\right)=A\left(x\right)+B\left(x\right)=6x^3-x-1+5x^3-2x+x^2-1=11x^3+x^2+x-2\)

\(b,Q\left(x\right)=A\left(x\right)-B\left(x\right)=6x^3-x-1-5x^3+2x-x^2+1=x^3-x^2+x\)

c, Ta có : \(2U\left(x\right)+2A\left(x\right)=B\left(x\right)\)

hay   \(2U\left(x\right)+2\left(6x^3-x-1\right)=5x^3-2x+x^2-1\)

\(\Rightarrow2U\left(x\right)+12x^3-2x-2=5x^3-2x+x^2-1\)

\(\Rightarrow2U\left(x\right)=5x^3-2x+x^2-1-12x^3+2x+2\)

\(\Rightarrow U\left(x\right)=-7x^3+x^2+1\)