Answer: All real numbers greater than or less than 9.
Step-by-step explanation: The range is possible y-values. In a parabola the range starts at a particular place then it either goes up or goes down. Since the leading factor has a negative in front of it, the parabola will open downward meaning most likely all y-values will be lest than the include max point. Now let find the max point using the formula -b/2a then substituting that into the parabola. -2/2(-1)= 1, then plug it in. y=-(1^2)+2(1)+8 which equal -1+2+8 which equal 9 so the max point is 9. Since the graph open downward all the points that are possible will either be at 9 or below it so the range is All real numbers greater than or less than 9. or (-∞,∞)∪(∞,9]