SOLUTION: please help me graph 3x^2 + 4y^2 -6x -24y +39=0

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Question 1015551: please help me graph 3x^2 + 4y^2 -6x -24y +39=0
Found 2 solutions by Edwin McCravy, ikleyn:
Answer by Edwin McCravy(20060) About Me  (Show Source):
You can put this solution on YOUR website!
3x%5E2%2B4y%5E2-6x-24y%2B39=0

This appears to be the equation of an ellipse:

3x%5E2-6x%2B4y%5E2-24y=-39

3%28x%5E2-2x%29%2B4%28y%5E2-6y%29=-39

Complete the square in the first parentheses on the left:
Coefficient of x is -2
Multiply it by 1/2, get -1
Square that: (-1)2 = +1
Add +1-1 inside the first parentheses on the end:

3%28x%5E2-2x%2B1-1%29%2B4%28y%5E2-6y%29=-39

Complete the square in the second parentheses on the left:
Coefficient of y is -6
Multiply it by 1/2, get -3
Square that: (-3)2 = +9
Add +9-9 inside the second parentheses on the end:

3%28x%5E2-2x%2B1-1%29%2B4%28y%5E2-6y%2B9-9%29=-39

Factor the first three terms in each parentheses as
the square of a binomial:

3%28%28x-1%29%5E2-1%29%2B4%28%28y-3%29%5E2-9%29=-39

Distribute the 3 and 4 into the outer parentheses 
leaving the two squares of binomials intact:

3%28x-1%29%5E2-3%2B4%28y-3%29%5E2-36=-39

3%28x-1%29%5E2%2B4%28y-3%29%5E2-39=-39

3%28x-1%29%5E2%2B4%28y-3%29%5E2=0

Normally we don't get a 0 on the right, and we divide
through by what we get.  But this is a rare case.  We
cannot divide by 0.  

Both terms are non-negative, so the left side must be 0.  
It can only be 0 if x=1 and y=3.

So this is the equation of the point (1,3).  It is really
an ellipse so small it has shrunk down to a point!

Here is the graph (Yes, that's all there is to it! One point!)



Edwin

Answer by ikleyn(52803) About Me  (Show Source):
You can put this solution on YOUR website!
.
please help me graph 3x^2 + 4y^2 -6x -24y +39=0
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Complete squares in x and y:

3x%5E2+%2B+4y%5E2+-6x+-24y+%2B39 = 3%28%28x-1%29%5E2+-+1%29+%2B+4%28%28y-3%29%5E2+-+9%29+%2B+39 = 3%28x-1%29%5E2+%2B+4%28y-3%29%5E2+%2B+39+-+3+-+36 = 3%28x-1%29%5E2+%2B+4%28y-3%29%5E2.

So, your equation is

3%28x-1%29%5E2+%2B+4%28y-3%29%5E2 = 0,   or

3%28x-1%29%5E2 = -4%28y-3%29%5E2.

This equation has the unique solution: x =1 and y=3.
There is no other real solutions.

So, the equation describes only one point (1,3).

The plot consists of only one point (1,3).