1.
`(2x+1/3)^3`
`= (2x)^3 + 3.(2x)^2 . 1/3 + 3.2x. (1/3)^2 + (1/3)^3`
`= 8x^3 + 4x^2 + 2/3 x + 1/27`
2.
a) `y^2 + 8y + 20`
`= y^2 + 2. y . 4 + 4^2 + 4`
`= (y^2 +4) + 4 > 0 \forall x`
b) `-x^2+6x-1 < 9`
`<=> -x^2 + 6x -10 < 0`
`<=> -(x^2 - 2.x.3 + 3^2) - 1 < 0`
`<=> -(x-3)^2 - 1 < 0 \forall x \in \mathbbR`