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Answer:
maximum: 8; no minimum
Explanation:
A graph can be useful. I find a graphing calculator handy. It shows the maximum of the function is f(-1) = 8. Since the parabola goes to -∞ for large values of x, there is no minimum.
maximum: 8
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You can also find the maximum by putting the function in vertex form.
-3(x^2 +2x) +5 . . . . factor the leading coefficient from the x terms
-3(x^2 +2x +1) +5 -(-3)(1) . . . . add the square of half the x-coefficient, subtract the equivalent amount
-3(x +1)^2 +8 . . . . . . the vertex form of the expression for f(x)
This form is ...
a(x -h)^2 +k . . . . . with a=-3, h=-1, k=8
so the vertex is (h, k) = (-1, 8) -- the same as shown on the graph. The negative value of 'a' tells you the parabola opens downward, so the vertex is the maximum. The maximum is 8 at x = -1.