Linear functions are the function which represents a straight line in graph.
A. y=2x-4
Here the graph drawn will be a straight line and thus it is a linear function.
B.
Here the equation is quadratic and thus would represent a parabola. So the function is not linear.
C. The table here shows that the value of y first increases with increase in x reaches zero and again decreases with increase in x. Thus the graph wouldnot be a straight line and thus it doesnot give a linear function.
D. The tble here shows y increases linearly with increase in x.Thus it would give us a linear function.
E.The graph here is a straight line and thus it is a linear function.
F.The graph here is a parabola and thus is non linear.
Thus the linear function are
A,D,F