Problem 5 · 2017 Math Kangaroo
Medium
Algebra & Patterns
evaluate-formula
Four of the following five pictures show pieces of the graph of the same quadratic function. Which piece does not belong?
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Answer: C
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Hint 1 of 2
All four matching pictures are slices of one single parabola, so they must agree on shape and where it crosses the axes.
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Hint 2 of 2
Find the quadratic that fits four of the slices; the fifth piece will be inconsistent with it.
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Approach: fit one quadratic to four of the slices and spot the odd one out
- Four of the five pictures are pieces of the very same parabola, so its roots and curvature must match in each.
- Reading the visible roots and turning behaviour, four of the slices are consistent with one quadratic.
- Piece C cannot lie on that same parabola, so it is the one that does not belong.
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