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- Mar 25th 2008, 09:42 AM #1

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## HELP.. someone [Solved]

Im stuck on this qustion:

Draw a suitable**straight**line on the grid (a grid is provided) to find estimates of the solutions of the equation...

x^2 - 3x - 6 = 0

(^ means "to the power of", So... x(to the power of 2) - 3x - 6 =0 )

Thanx to anyone who can help me out. i have no idear what to do

- Mar 25th 2008, 10:04 AM #2

- Mar 25th 2008, 10:08 AM #3

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- Mar 25th 2008, 11:10 AM #4

- Mar 25th 2008, 12:41 PM #5

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- Mar 25th 2008, 01:50 PM #6

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If I had to take a stab at why the x-coordinates used were -2 and -1, I'd say because you can determine that the x-intercept is between those two x-values. Note that, for your original function, f(-2) is positive and f(-1) is negative. This means, since the function is continuous, i.e., doesn't have any holes, gaps, jumps, etc, that it must cross the x-axis somewhere between there. -2 and -1 provide nice integer values to use when creating your line of approximation.

- Mar 25th 2008, 02:09 PM #7

- Mar 25th 2008, 02:33 PM #8

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- Mar 25th 2008, 02:55 PM #9

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Drawing a single line to approximate BOTH "sides" of a parabola seems like an awful idea. I've got to assume the teacher meant one line per x-intercept. A single line could not possibly approximate both intercepts at once because a single line will only cross the x-axis ONCE (unless that line IS the x-axis, in which case it is equally useless as an approximation).

- Mar 25th 2008, 03:02 PM #10

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thanx everyone, this is from an IGCSE exam taken by thousands of pupils around the world. They try to be very clear in there questions. To stop problems such as these occurring.

If no-one can reach an 100% sure answer, ill be going bk to school on next Tuesday ill post the answer here. tanx again

- Mar 26th 2008, 04:49 PM #11

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- Mar 26th 2008, 05:07 PM #12

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- Mar 27th 2008, 03:06 AM #13

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