a) `f(x) + g(x) = 5x^2 - 2x+5 +5x^2 - 6x -1/3`
`f(x) + g(x)= (5x^2 + 5x^2) - (2x+6x) + (5-1/3)`
`f(x) + g(x) = 10x^2 - 8x +14/3`
b) `f(x) - g(x)= 5x^2 - 2x+ 5 - 5x^2 +6x + 1/3`
`f(x) - g(x) = (5x^2 - 5x^2) - (2x - 6x) + (5+1/3)`
`f(x) - g(x)= 4x + 16/3`
c) Xét `f(x) - g(x) =0`
`=> 4x + 16/3 = 0`
`=> 4x = -16/3`
`=> x= -16/3 : 4`
`=>x = -16/3 . 1/4`
`=> x= -4/3`
Vậy nghiệm của `f(x) - g(x)` là `-4/3`
