Answer:
√5
Step-by-step explanation:
The distance from the given point to the curve can be found using the distance formula. The resulting expression can be minimized to find the minimum distance.
d = √((x2 -x1)² +(y2 -y1)²)
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Point on the Parabola
A point on the parabola can be described by ...
x -y² = 0
x = y² . . . . . add y²
Then a point on this curve is ...
(y², y)
Distance to Given Point
The distance to it from (0, 3) is ...
d = √((0 -y²)² +(3 -y)²) = √(y⁴ +y² -6y +9)
Find the Minimum
The distance will be minimized when the derivative of the radical expression is zero:
d(y⁴ +y² -6y +9)/dy = 0 = 4y³ +2y -6
0 = 2y³ +y -3 . . . . . . . . remove a factor of 2
This will have a rational root in the set {±1, ±3}.
Trial and error shows that y=1 is the only real solution to this equation.
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Then the minimum distance is ...
d = √(1⁴ +1² -6·1 +9) = √5
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Additional comment
The attached graph shows that a circle with radius √5 centered at (0, 3) will intersect the parabola at exactly one point. That confirms our solution.
