Math  /  Geometry

Question1. What is the equation, center, and radius of the circle? x2+2x+y2+6y7=0x2+2x+y2+6y=7x2+2x+17y2+6y=7+1(x+1)2+y2+6y=8(x+1)2+y2+6y+9<8+9(x+1)2+(y+3)2=17\begin{array}{l} x^{2}+2 x+y^{2}+6 y-7=0 \\ x^{2}+2 x+y^{2}+6 y=7 \\ x^{2}+2 x+17 y^{2}+6 y=7+1 \\ (x+1)^{2}+y^{2}+6 y=8 \\ (x+1)^{2}+y^{2}+6 y+9<8+9 \\ (x+1)^{2}+(y+3)^{2}=17 \end{array}

Studdy Solution

STEP 1

1. The given equation is a quadratic equation representing a circle.
2. The equation needs to be rewritten in the standard form of a circle's equation to identify the center and radius.

STEP 2

1. Rearrange the given equation.
2. Complete the square for both xx and yy.
3. Rewrite the equation in the standard form of a circle.
4. Identify the center and radius from the standard form.

STEP 3

Rearrange the given equation to group xx and yy terms:
x2+2x+y2+6y=7 x^2 + 2x + y^2 + 6y = 7

STEP 4

Complete the square for the xx terms:
x2+2x x^2 + 2x
To complete the square, take half of the coefficient of xx, square it, and add it inside the equation:
(22)2=1 \left(\frac{2}{2}\right)^2 = 1
Add and subtract 1:
(x2+2x+1)1 (x^2 + 2x + 1) - 1
This becomes:
(x+1)21 (x + 1)^2 - 1

STEP 5

Complete the square for the yy terms:
y2+6y y^2 + 6y
To complete the square, take half of the coefficient of yy, square it, and add it inside the equation:
(62)2=9 \left(\frac{6}{2}\right)^2 = 9
Add and subtract 9:
(y2+6y+9)9 (y^2 + 6y + 9) - 9
This becomes:
(y+3)29 (y + 3)^2 - 9

STEP 6

Rewrite the equation in the standard form of a circle:
Substitute the completed squares back into the equation:
(x+1)21+(y+3)29=7 (x + 1)^2 - 1 + (y + 3)^2 - 9 = 7
Simplify:
(x+1)2+(y+3)2=17 (x + 1)^2 + (y + 3)^2 = 17

STEP 7

Identify the center and radius from the standard form:
The standard form of a circle is:
(xh)2+(yk)2=r2 (x - h)^2 + (y - k)^2 = r^2
From the equation:
(x+1)2+(y+3)2=17 (x + 1)^2 + (y + 3)^2 = 17
The center (h,k)(h, k) is (1,3)(-1, -3) and the radius rr is 17\sqrt{17}.
The equation of the circle is:
(x+1)2+(y+3)2=17 (x + 1)^2 + (y + 3)^2 = 17
The center of the circle is:
(1,3) (-1, -3)
The radius of the circle is:
17 \sqrt{17}

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