Draw the line `y=x` on the given graph `y= f(x)`.
From the figure, `xf(x) gt 0` for `x in (-3, -2) uu (-1, 0) uu (0, 1) uu (2, 3) uu (4,5) and xf(x) lt 0` for `x in (-4, -3) uu (-2, -1)uu (1, 2) uu (3, 4) uu ( 5, 6)`
`" "xf(x) = 0` for `x=-4, -3, -2, -1, 0, 1, 2, 3, 4, 5, 6`
Thus, the graph of `y= f(x) = "sgn"(xf(x))` is as follows.
