The combined height of one fir tree and one pine tree is 21 meters. the height of 4 fir trees stacked on top of each other is 24 meters taller than one pine tree

This needs to be done quick you are studying different function tools and begin working with this function y=-160-9(x) use the equation to answer the question y=-160-9(x) what is the y value when x equals -13? y=-160-9(x)

When turned about its axis of rotation, which shape could have created this three-dimensional object?

[10 points, algebra 2]according to my answer key the restrictions are -1 and 4. but why not positive 1?