SOLUTION: Find the standard equation,foci,asymptotes and vertices of 25x^2-39y^2+150x+390y=-225

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Question 1043331: Find the standard equation,foci,asymptotes and vertices of 25x^2-39y^2+150x+390y=-225
Answer by KMST(5328) About Me  (Show Source):
You can put this solution on YOUR website!
25x%5E2-39y%5E2%2B150x%2B390y=-225
25x%5E2%2B150x-39y%5E2%2B390y=-225
25%28x%5E2%2B6x%29-39%28y%5E2-10y%29=-225
25%28x%5E2%2B6x%2B9%29-39%28y%5E2-10y%2B25%29=-225%2B25%2A9-39%2A25
25%28x%5E2%2B6x%2B9%29-39%28y%5E2-10y%2B25%29=-225%2B225-975
25%28x%2B3%29%5E2-39%28y-5%29%5E2=-975
39%28y-5%29%5E2-25%28x%2B3%29%5E2=975
39%28y-5%29%5E2%2F975-25%28x%2B3%29%5E2%2F975=975%2F975
highlight%28%28y-5%29%5E2%2F25-%28x%2B3%29%5E2%2F39=1%29
The standard equation above tells us that
the center is at (-3,5) ;
the major (or transverse) axis is x=-3;
the focal distance is c=sqrt%2825%2B39%29=sqrt%2864%29=8 ;
the asymptotes have slopes such that slope%5E2=25%2F39 , and
the y-coordinates of the vertices can be found from
%28y-5%29%5E2%2F25=1 .
The asymptotes pass through center %22%28-3+%2C+5+%29%22 ,
and have slopes such as
slope%5E2=25%2F39-->system%28slope=5sqrt%2839%29%2F39%2C%22or%22%2Cslope=-5sqrt%2839%29%2F39%29 ,
the equations of the asymptotes (in point-slope form) are
highlight%28y-5=5sqrt%2839%29%28x%2B3%29%2F39%29 and highlight%28y-5=-5sqrt%2839%29%28x%2B3%29%2F39%29 .
Those equations can also be written as
highlight%28y=-5sqrt%2839%29x%2F39%2B%2865-15sqrt%2839%29%29%2F13%29 and
highlight%28y=5sqrt%2839%29x%2F39%2B%2865%2B15sqrt%2839%29%29%2F13%29 in slope-intercept form.
Since the foci are on the major axis,
at a distance c=8 from the center,
their y- coordinates are y=5+%2B-+8 , or system%28y=5%2B8=13%2C%22or%22%2Cy=5-8=-3%29 .
So, one focus is at highlight%28%22%28+-3+%2C+13+%29%22%29 ,
and the tother focus is at highlight%28%22%28+-3+%2C+-3+%29%22%29
As for the vertices, also on the major axis,
%28y-5%29%5E2%2F25=1-->%28y-5%29%5E2=25-->y=5+%2B-+sqrt%2825%29=+5+%2B-+5---> y=10%2C%22or%22%2Cy=0%29 .
So the vertices are at highlight%28%22%28+-3+%2C+10+%29%22%29 and highlight%28%22%28+-3+%2C+0+%29%22%29 .
The hyperbola with major axis and foci looks like this: