Asking when the function is negative is just asking when the graph itself is negative (aka, when the graph is below the x-axis (the horizontal one)).
For this graph, the graph is below the x-axis (is negative) at every x value up until 1. You can see that after x=1, the graph is now above the x-axis, meaning it is positive.
An easy way to think about it is just remembering: if the graph is above the horizontal axis (x-axis), then it is positive, and if it is below the horizontal axis then it is negative.
(Let me know if you want me to explain something more!)