Easy# Not a Linear Combination

LINALG-XBGHIZ

Which of the following statements are *FALSE*?

$(i)$ $2 x^2 +3x^3 -2 x^4$ is a linear combination of $x^2, x^3, x^4$

$(ii)$ $3 x^2-x+1$ is a linear combination of $x^2, x, 1$

$(iii)$ $\sqrt x+{1\over 3} y$ is a linear combination of $x$ and $y$

$(iv)$ $\sin x+ \cos y$ is a linear combination of $x$ and $y$