I'm struggling to solve this proof:
Suppose that $u_1, u_2, . . . , u_n$$\boldsymbol{u}_1, \boldsymbol{u}_2, . . . , \boldsymbol{u}_n$ are solutions of an homogeneous system of linear equations $A$x$ = 0, $x$ ∈ R$$\boldsymbol{Ax} = \boldsymbol{0}$, $\boldsymbol{x} \in \mathbb{R}^n$.
Suppose that $k_i ∈ R$$k_i \in \mathbb{R}$. Show that
$k_1u_1 + k_2u_2 + · · · + k_nu_n$$k_1\boldsymbol{u}_1 + k_2\boldsymbol{u}_2 + · · · + k_n\boldsymbol{u}_n$
is also a solution of the system $A$x$ = 0$$\boldsymbol{Ax}=\boldsymbol{0}$.
I know that I should use the proof for showing that if A is invertible then the only solution is $$x$=0$$\boldsymbol{x}=\boldsymbol{0}$ when $A$x$=0$$\boldsymbol{Ax}=\boldsymbol{0}$, but am unsure about the most efficient way of doing this.
Any help is greatly appreciated.