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| Question 216624:  9x^2 + 16y^2 - 18x + 64y - 71 = 0
 find the coordinates of the center.
 a)(1,2)
 b)(1,-2)
 c)(-1,2)
 d)(-2,1)
 Found 2 solutions by  RAY100, crystal_nguyen:
 Answer by RAY100(1637)
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You can put this solution on YOUR website! 9x^2 -18x  +  16y^2 +64y = 71 .
 9(x^2 -2x ) + 16(y^2 +4y ) = 71,,,complete  the  squares  remembering  the  last  term  = (2nd  term / 2) squared,,,,,and  add  compensating  amt  to  opposite  side  of  eqn
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 9(x^2 -2x +1) +16(y^2 +4y+4) = 71 +(9*1) + (16*4) = 144
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 9(x-1)^2 +16(y+2)^2 =144,,,,   divide  by  144
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 (1/16){(x-1)^2}  + (1/9){(y+2)^2} = 1
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 {(x-1)^2} / 16 + {(y+2)^2} / 9 =1,,,,,,,which  is  eqn  for  ellipse
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 Center  is  at  (1,-2),,,,,,,which  is  answer  (b)
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Answer by crystal_nguyen(2)
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