To find #g(1)# substitute #color(red)(1)# for each occurrence of #color(red)(x)# in #g(x)#:
#g(color(red)(x)) = color(red)(x)^3 + color(red)(x)^2 - 6color(red)(x)# becomes:
#g(color(red)(1)) = color(red)(1)^3 + color(red)(1)^2 - (6 * color(red)(1))#
#g(color(red)(1)) = 1 + 1 - 6#
#g(color(red)(1)) = -4#
To find #g(-1)# substitute #color(red)(-1)# for each occurrence of #color(red)(x)# in #g(x)#:
#g(color(red)(x)) = color(red)(x)^3 + color(red)(x)^2 - 6color(red)(x)# becomes:
#g(color(red)(-1)) = color(red)(-1)^3 + color(red)(-1)^2 - (6 * color(red)(-1))#
#g(color(red)(1)) = -1 + 1 + 6#
#g(color(red)(1)) = 6#