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Equation of a circle questions. please help?

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hi, please help me with these 2 problems. thanks.

Find the radius and the coordinates of the center of the circle for each question.
4(x-3)^2 + 4(y-2)^2=10

Write the standard form of the equation.
x^2 + y^2 + x = 3/4
asked Jun 25, 2014 in PRECALCULUS by anonymous

2 Answers

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1) The circle equation is 4(x - 3)2 + 4(y - 2)2  = 10.

The standard form of the circle equation is ( x - h )2 + ( y - k )2 = r2, where, (h, k) is the center of the circle, and r is the radius.

Write the equation in standard form of a circle.

Here x 2 and y 2coefficient is 4 , for perfect square make x 2and y 2 coefficient 1 by dividing each side by 4.

[4(x - 3)2]/4 + [4(y - 2)2]/4  = 10/4

(x - 3)2+ (y - 2)2  = 5/2

(x - 3)2+ (y - 2)2  = [√(5/2)]2

Compare the equation with standard form of a circle equation.

The center (h, k) is (3, 2), and

The radius (r) is √(5/2) units.

answered Jun 25, 2014 by david Expert
0 votes

2) The circle equation is x2 +  y2 + x = 3/4.

x2 + x + y2  = 3/4.

The standard form of the circle equation is ( x - h )2 + ( y - k )2 = r2, where, (h, k) is the center of the circle, and r is the radius.

Write the equation in standard form of a circle.

To change the expression into a perfect square  add (half the x coefficient)² and add (half the y coefficient)²to each side of the expression.

Here, x coefficient = 1, so, (half the x coefficient)² = (1/2)2= 1/4.

Here, y coefficient = 0, so, (half the y coefficient)² = (0)2= 0.

Add 1/4 and 0 to each side.

x2 +  x + 1/4 + y2 + 0 = 3/4 + 1/4 + 0

(x + 1/2)2 + (y - 0)2  = 1

[x - (- 1/2)]2 + (y - 0)2  = 12

Compare the equation with standard form of a circle equation.

The center (h, k) is (-1/2, 0), and

The radius (r) is 1 unit.

 

answered Jun 25, 2014 by david Expert

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