Engineering Board Exam Reviewer · Parabolas · hard
Find the equation of the parabola with a vertical axis that passes through (0,0), (2,0) and (-1,3).
- x2 + 2 x - y = 0
- x2 - 2 x - y = 0
- x2 - x - y = 0
- x2 - 2 x + y = 0
Answer
B. x2 - 2 x - y = 0
Solution
Let y=ax2+bx+c. (0,0) c=0; (2,0) 4a+2b=0; (-1,3) a-b=3. Solving gives a=1, b=-2, so y=x2-2x.
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