`a)`
`P(x)=-12x^2+34x^4-12x^3-14x+2x^5`
`=2x^5+34x^4-12x^3-12x^2-14x`
``
`Q(x)=0,5x^2+12x^4-2x^3-14-2x^5`
`=-2x^5+12x^4-2x^3+0,5x^2-14`
``
`b)`
`P(x)+Q(x)`
`=(2x^5+34x^4-12x^3-12x^2-14x)+(-2x^5+12x^4-2x^3+0,5x^2-14)`
`=2x^5+34x^4-12x^3-12x^2-14x-2x^5+12x^4-2x^3+0,5x^2-14`
`=(2x^5-2x^5)+(34x^4+12x^4)+(-12x^3-2x^3)+(-12x^2+0,5x^2)-14x-14`
`=46x^4-14x^3-23/2x^2-14x-14`
``
`P(x)-Q(x)`
`=(2x^5+34x^4-12x^3-12x^2-14x)-(-2x^5+12x^4-2x^3+0,5x^2-14)`
`=2x^5+34x^4-12x^3-12x^2-14x+2x^5-12x^4+2x^3-0,5x^2+14`
`=(2x^5+2x^5)+(34x^4-12x^4)+(-12x^3+2x^3)+(-12x^2-0,5x^2)-14x+14`
`=4x^5+22x^4-10x^3-25/2x^2-14x+14`