Answer :
You're given that
[tex]\mathbf{Ax}_1=\mathbf b[/tex]
and
[tex]\mathbf{Ax}_0=\mathbf0[/tex]
Adding both systems together gives
[tex]\mathbf{Ax}_1+\mathbf{Ax}_0=\mathbf b+\mathbf 0[/tex]
[tex]\mathbf A(\mathbf x_1+\mathbf x_0)=\mathbf b[/tex]
which means [tex]\mathbf x_1+\mathbf x_0[/tex] is also a solution to [tex]\mathbf{Ax}=\mathbf b[/tex].
[tex]\mathbf{Ax}_1=\mathbf b[/tex]
and
[tex]\mathbf{Ax}_0=\mathbf0[/tex]
Adding both systems together gives
[tex]\mathbf{Ax}_1+\mathbf{Ax}_0=\mathbf b+\mathbf 0[/tex]
[tex]\mathbf A(\mathbf x_1+\mathbf x_0)=\mathbf b[/tex]
which means [tex]\mathbf x_1+\mathbf x_0[/tex] is also a solution to [tex]\mathbf{Ax}=\mathbf b[/tex].