Quadratic equation

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March 15th 2011, 03:10 PM
Bluerabbits

Quadratic equation

A stuntman is being shot out of a canon. He´s following a track that is determinded by this equation:

y = 1 + 3x - 0,05x^2

where x meter is the horizontal distance from the canon and y meter is the height.
Will the stuntman be able to cross a gulch that is 58 metres wide?

Picture (I drew xD):

http://i56.tinypic.com/33jjvco.png

OPS! 56 m bred (swedish word for: width)

56 m bred = 56 m width
March 15th 2011, 03:25 PM
pickslides

You mean $y = 1 + 3x - 0.05x^2$ ?

What were your solutions for y=0?
March 16th 2011, 02:03 AM
Bluerabbits

I don´t know how to solve this ...
March 16th 2011, 02:23 AM
HallsofIvy

That's a quadratic equation, as you say, so use the quadratic formula:
The solutions to $ax^2+ bx+ c= 0$ are given by
$\frac{-b\pm\sqrt{b^2- 4ac}}{2a}$ .

Here, a= -0.05, b= 3, and c= 1.
March 16th 2011, 03:23 AM
Bluerabbits

Quote:

Originally Posted by HallsofIvy

That's a quadratic equation, as you say, so use the quadratic formula:
The solutions to $ax^2+ bx+ c= 0$ are given by
$\frac{-b\pm\sqrt{b^2- 4ac}}{2a}$ .

Here, a= -0.05, b= 3, and c= 1.

Hi, I have been trying to put this into my calculator but it´s just saying error all the time ...
March 16th 2011, 10:27 AM
topsquark

Quote:

Originally Posted by Bluerabbits

Hi, I have been trying to put this into my calculator but it´s just saying error all the time ...

Try it this way. Find $b^2 - 4ac$ . Then take the square root. Then calculate the rest. If you break it apart there's less chance of a calculation error. Just make sure you don't round off the intermediate steps. Keep, say, at least 5 digits.

-Dan

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