\(A=x^4+6x^2+8x^3-2x-3\)
\(B=3x^2+x^4+4x^3-3x+5\)\(\Rightarrow2B=6x^2+2x^4+8x^3-6x+10\)
\(\Rightarrow A-2B=x^4+6x^2+8x^3-2x-3\)\(-6x^2-2x^4-8x^3+6x-10\)
\(=-x^4+4x-13\)
Ta có
\(A=x^4+8x^3+6x^2-2x-3\)
\(B=x^4+4x^3+3x^2-3x+5\Rightarrow2B=2x^4+8x^3+6x^2-6x+10\)
\(A-2B=x^4+8x^3+6x^2-2x-3\)\(-2x^4-8x^3-6x^2+6x-10\)
\(A-2B=-x^4+4x-13\)