To find the roots, let y=0 and find the places where the graph crosses the x-axis. When y=0, (8-x)lnx =0. This can be solved by splitting the terms and putting each =0. This is because if the answer is 0, one or both of the two things multiplied together must be equal to 0. Therefore, (8-x)=0 and lnx=0. These solve to give x=8 and x=1.