[futurebasic] Re: Coordinate geometry.

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From: wave@... (Mark Goodes)
Date: Thu, 11 Dec 1997 19:39:22 -0500
Instead of parsing the equations, you might try to emulate the steps.
Assuming you know the slope of each line and a point on it, you could try
the translation that is written to the right of each algebraic step below.
ex:  5(x-2)+1=7(x-3)-2    ' two sample equations in slope-point form
       Prepare equations:
       5(x-2)+1
      =5x-10+1     'multiply the x value of the known point by the slope
      =5x-11           'add the result to the y-value and save the new
y-value as a "y-intercept 1"
      Same for the other equation:
        7(x-3)-2
        =7x-21-2
        =7x-23
       We now have
        5x-11=7x-23
        -2x-11=-23   'subtract second slope from first and save it as a
slope result
        -2x=-12    'subtract first y-intercept from second and save the result
        x=6     'divide the above result by the slope result
        This gives the x-value of the point of intersection. To get the
y-value, sub this result back into one of the above expressions:
        y=5(6)-11
        y=30-11   'multiply the x value by the original slope of line 1
        y=19    'subtract the y-intercept of line 1
This gives a point of intersection of (6, 19).
Using the above commented steps, you can avoid any algorithmic equation
solving and just use simple arithmetic steps.  If this is still too
obscure, let me know and I'll try to translate it into FB code.  Hope this
helps.


>Find x where they intersect
>
>3x + 2 = -4x
>     2 = -7x
>  -2/7 = x

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Mark Goodes (wave@...)