Ответ: \[8x^{2} - x + 3 + \left( - 2x^{2} + 4x - 5 \right) =\] \[= 8x^{2} - x + 3 - 2x^{2} + 4x - 5 =\] \[= 6x^{2} + 3x - 2.\]