a)Ta có:
\(P\left(x\right)+Q\left(x\right)=\left(3x^2+5x+1\right)+\left(2x^2+4x+2\right)\)
\(=3x^2+5x+1+2x^2+4x+2\)
\(=\left(3x^2+2x^2\right)+\left(5x+4x\right)+\left(1+2\right)\)
\(=5x^2+9x+3\)
b) Ta có:
\(A\left(x\right)-B\left(x\right)=\left(3x^2+2x-4\right)-\left(-3x^2-2x+3\right)\)
\(=3x^2+2x-4+3x^2+2x-3\)
\(=\left(3x^2+3x^2\right)+\left(2x+2x\right)-\left(4+3\right)\)
\(=6x^2+4x-7\)
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