(1,5 điểm) Thực hiện phép tính: (a) 2x(x^2+3x−5). (b) (4x^4+2x^6+12x^8):(2x^2). (c) (x+1)(2x+1)−2x^2.

a) \(2x\left( {{x^2} + 3x - 5} \right) = 2{x^3} + 6{x^2} - 10x\)

\[\begin{array}{l}b)\left( {4{x^4} + 2{x^6} + 12{x^8}} \right):\left( {2{x^2}} \right)\\ = 2{x^2} + {x^4} + 6{x^6}\end{array}\]

\(\begin{array}{l}c)\left( {x + 1} \right)\left( {2x + 1} \right) - 2x{}^2\\ = 2{x^2} + 3x + 1 - 2{x^2}\\ = 3x + 1\end{array}\)