Q. A circle in the xy-plane has the equation 4x2+4y2−24x=28. What is the diameter of the circle?□
Complete the square for x-terms: First, we need to complete the square for the x-terms in the equation.4x2−24x can be written as 4(x2−6x).To complete the square, we add (6/2)2=9 to the expression inside the parenthesis.So, we have 4(x2−6x+9).
Add to balance the equation: We also need to add 4×9 to the other side of the equation to keep it balanced.The equation becomes 4(x2−6x+9)+4y2=28+4×9.
Simplify the equation: Now, simplify the equation.4(x−3)2+4y2=28+36.4(x−3)2+4y2=64.
Divide by 4 for standard form: Divide the whole equation by 4 to get the standard form of the circle's equation.(x−3)2+y2=16.
Identify center and radius: The standard form of a circle's equation is (x−h)2+(y−k)2=r2, where (h,k) is the center and r is the radius.From our equation, r2=16, so r=4.
Calculate the diameter: The diameter of a circle is twice the radius.So, the diameter is 2×4=8.