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x^(2)+y^(2)+6x-4y=3
A circle in the 
xy-plane has the equation shown. What is the 
y coordinate of the center of the circle?

x2+y2+6x4y=3 x^{2}+y^{2}+6 x-4 y=3 \newlineA circle in the xy x y -plane has the equation shown. What is the y y coordinate of the center of the circle?

Full solution

Q. x2+y2+6x4y=3 x^{2}+y^{2}+6 x-4 y=3 \newlineA circle in the xy x y -plane has the equation shown. What is the y y coordinate of the center of the circle?
  1. Rewriting the equation: To find the center of the circle, we need to rewrite the equation in the standard form of a circle, which is (xh)2+(yk)2=r2(x - h)^2 + (y - k)^2 = r^2, where (h,k)(h, k) is the center of the circle. We will complete the square for both xx and yy.
  2. Grouping the terms: First, we group the x terms and the y terms together: (x2+6x)+(y24y)=3(x^2 + 6x) + (y^2 - 4y) = 3.
  3. Completing the square for x terms: To complete the square for the x terms, we take half of the coefficient of x, which is \frac{66}{22} = 33, and square it, adding 33^22 = 99 to both sides of the equation.
  4. Completing the square for y terms: Similarly, to complete the square for the y terms, we take half of the coefficient of y, which is -\frac{44}{22} = 2-2, and square it, adding (2-2)^22 = 44 to both sides of the equation.
  5. Adding constants to both sides: Now we add 99 and 44 to both sides of the equation to maintain equality: (x2+6x+9)+(y24y+4)=3+9+4(x^2 + 6x + 9) + (y^2 - 4y + 4) = 3 + 9 + 4.
  6. Simplifying the right side: Simplify the right side of the equation: 3+9+4=163 + 9 + 4 = 16.
  7. Standard form of the equation: The equation now looks like this: (x2+6x+9)+(y24y+4)=16(x^2 + 6x + 9) + (y^2 - 4y + 4) = 16.
  8. Finding the center of the circle: We can now rewrite the equation as (x+3)2+(y2)2=16(x + 3)^2 + (y - 2)^2 = 16, which is in the standard form of a circle.
  9. The y-coordinate of the center: From the standard form (x+3)2+(y2)2=16(x + 3)^2 + (y - 2)^2 = 16, we can see that the center of the circle is at (3,2)(-3, 2).
  10. The y-coordinate of the center: From the standard form (x+3)2+(y2)2=16(x + 3)^2 + (y - 2)^2 = 16, we can see that the center of the circle is at (3,2)(-3, 2).The y-coordinate of the center of the circle is 22.

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