A function is denoted as y = g (x), where x is the argument or input of the function. We know that x=-1, this means that in order to get g(-1) we should replace x with -1.
g(-1)=(-1)^3+6(-1)^2+12*(-1)+8= (-1)+6*1+(-12)+8=-1+6-12+8=5-12+8=-7+8=1
g(-1)=1
