Question

4x+4y+z=242x-4y+z=05x-4y-5z=12

Answer 1

`\begin{gathered} 4x+4y+z=24 \\ -2(2x-4y+z=0) \\ \text{the you have:} \\ \\ 4x+4y+z=24 \\ -4x+8y-2z=0 \\ 12y-z=24 \\ \text{with the second and third:} \\ 5(2x-4y+z=0) \\ -2(5x-4y-5z=12​) \\ \text{which gives:} \\ 10x-20y+5z=0 \\ -10x+8y+10z=-24 \\ by\text{ addings these equations, one has:} \\ -12y+15z=-24 \\ \text{add:} \\ 12y-z=24 \\ -12y+15z=-24 \\ \text{which gives:} \\ 14z=0,\text{ so z=0} \end{gathered}`