Section 6.2

Determining the Type and Position of a Second-Order Curve from Its Equation

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Problem 532

Find the foci and directrices of the rectangular (equilateral) hyperbola 2xy=a22 x y = a^{2}.

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Problem 533

Find the foci of the hyperbola:

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(1)

x225−y2144=1\frac{x^{2}}{25}-\frac{y^{2}}{144} = 1;

(2)

x2225−y264=−1\frac{x^{2}}{225}-\frac{y^{2}}{64} = -1.

Problem 534

Find the coordinates of the focus of the parabola x2=4yx^{2} = 4 y.

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Problem 535

Set up the equation of the directrix of the parabola y2=6xy^{2} = 6 x.

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Problem 536

Find the foci and corresponding directrices of the following curves:

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(1)

x24+y220=1\frac{x^{2}}{4}+\frac{y^{2}}{20} = 1;

(2)

x24−2y2+8=0\frac{x^{2}}{4}-2 y^{2}+8 = 0;

(3)

y=34x2y = \frac{3}{4} x^{2}.

Problem 537

Using a translation of the coordinate axes, find the canonical equation and determine the position of the second-order curves given by the equations:

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(1)

x2+2y2+4x−4y=0x^{2}+2 y^{2}+4 x-4 y = 0

(2)

4x2−y2−8x−6y−4=04 x^{2}-y^{2}-8 x-6 y-4 = 0;

(3)

4x2+4x+2y−1=04 x^{2}+4 x+2 y-1 = 0

(4)

6x2+8y2+3x−4y+1=06 x^{2}+8 y^{2}+3 x-4 y+1 = 0;

(5)

2x2−3y2−6x+9y−2=02 x^{2}-3 y^{2}-6 x+9 y-2 = 0;

(6)

2x2+6x+3y+6=02 x^{2}+6 x+3 y+6 = 0;

(7)

4y2+4x−2y+1=04 y^{2}+4 x-2 y+1 = 0;

(8)

3x2−2y2+6x+4y+1=03 x^{2}-2 y^{2}+6 x+4 y+1 = 0.

Problem 538

Find the centers of the following second-order curves:

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(1)

5x2+8xy+5y2−18x−18y+11=05 x^{2}+8 x y+5 y^{2}-18 x-18 y+11 = 0;

(2)

2xy−4x+2y+11=02 x y-4 x+2 y+11 = 0;

(3)

4x2+4xy+y2−10x−5y+6=04 x^{2}+4 x y+y^{2}-10 x-5 y+6 = 0;

(4)

x2−2xy+y2−3x+2y−11=0x^{2}-2 x y+y^{2}-3 x+2 y-11 = 0.

Problem 539

Find the canonical form and the formulas relating the original coordinates to the canonical ones, for the following second-order curves:

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(1)

(x+y−1)22+(x−y+3)28+1=0\frac{(x+y-1)^{2}}{2}+\frac{(x-y+3)^{2}}{8}+1 = 0;

(2)

(x+2y+1)2+4x−2y−6=0(x+2 y+1)^{2}+4 x-2 y-6 = 0;

(3)

(x+2y+1)2+x−3y−6=0(x+2 y+1)^{2}+x-3 y-6 = 0;

(4)

(x−3y+2)210−(3x+y+1)220+20x=0\frac{(x-3 y+2)^{2}}{10}-\frac{(3 x+y+1)^{2}}{20}+20 x = 0.

Problem 540

Determine the canonical form and canonical coordinate system of the following second-order curves:

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(1)

5x2+4xy+8y2−32x−56y+80=05 x^{2}+4 x y+8 y^{2}-32 x-56 y+80 = 0;

(2)

5x2+8xy+5y2−18x−18y+9=05 x^{2}+8 x y+5 y^{2}-18 x-18 y+9 = 0;

(3)

5x2+6xy+5y2−16x−16y−16=05 x^{2}+6 x y+5 y^{2}-16 x-16 y-16 = 0;

(4)

12xy+5y2−12x−22y−19=012 x y+5 y^{2}-12 x-22 y-19 = 0;

(5)

7x2+16xy−23y2−14x−16y−218=07 x^{2}+16 x y-23 y^{2}-14 x-16 y-218 = 0;

(6)

7x2−24xy−38x+24y+175=07 x^{2}-24 x y-38 x+24 y+175 = 0;

(7)

9x2+24xy+16y2−40x+30y=09 x^{2}+24 x y+16 y^{2}-40 x+30 y = 0;

(8)

x2+2xy+y2−8x+4=0x^{2}+2 x y+y^{2}-8 x+4 = 0

(9)

4x2−4xy+y2−2x−14y+7=04 x^{2}-4 x y+y^{2}-2 x-14 y+7 = 0.

Problem 541

In a rectangular coordinate system, a second-order curve is given by the equation 6xy+8y2−12x−26y+11=06 x y+8 y^{2}-12 x-26 y+11 = 0.

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(1)

Reduce the given equation to canonical form.

(2)

Find the relation between the old coordinates xx and yy and the new (canonical) coordinates x′x^{\prime } and y′y^{\prime }.

(3)

Find the coordinates of the center, vertices, and foci of this curve relative to the original coordinate system.

(4)

Set up the equations of the directrices, asymptotes, and tangents at the vertices of this curve in the original coordinate system.