SOLUTION: The bulb of the parabolic flashlight should be placed in its focus. If the flashlight is 15 cm deep and 42 cm wide in the opening, how far should the bulb be to the vertex of the p

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Question 1169506: The bulb of the parabolic flashlight should be placed in its focus. If the flashlight is 15 cm deep and 42 cm wide in the opening, how far should the bulb be to the vertex of the parabola?
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
Imagining vertex (0,0) and a minimum point, symmetry axis x=0.
then parabola also will have (-21,15) and (21,15).

75y%2F7=x%5E2

Focus, if some p units above the vertex,
4p=75%2F7
p=75%2F28

p=2.68 centimeters