Cho hai đa thức: \(\begin{array}{l}M\left( x \right) = 3{x^4} - 2{x^3} + {x^2} + 4x - 5\\N\left( x \right) = 2{x^3} + {x^2} - 4x - 5\end{

a)

\(\begin{array}{l}
M\left( x \right) = 3{x^4} - 2{x^3} + {x^2} + 4x - 5;N\left( x \right) = 2{x^3} + {x^2} - 4x - 5\\
M\left( x \right) + N\left( x \right) = 3{x^4} + \left( { - 2{x^3} + 2{x^3}} \right) + \left( {{x^2} + {x^2}} \right) + \left( {4x - 4x} \right) + \left( { - 5 - 5} \right) = 3{x^4} + 2{x^2} - 10
\end{array}\)

b) \(P\left( x \right) = M\left( x \right) - N\left( x \right) = 3{x^4} - 4{x^3} + 8x\)