Q. A circle in the xy-plane has the equation2x2+2y2−8x−5y−855=0. What is the diameter of the circle?
Rewrite Equation: Rewrite the given equation of the circle in a more standard form by completing the squares for x and y. 2x2+2y2−8x−5y−855=0Divide the entire equation by 2 to simplify the coefficients of x2 and y2. x2+y2−4x−25y−1655=0
Complete Squares:Complete the square for the x-terms.Add (24)2=4 to both sides of the equation to complete the square for x.x2−4x+4+y2−(25)y−(1655)=4
Combine Terms: Complete the square for the y-terms.Add (2(25))2 = 1625 to both sides of the equation to complete the square for y.x2−4x+4+y2−25y+1625−1655=4+1625
Identify Radius: Combine like terms and rewrite the equation in standard form.(x−2)2+(y−45)2=4+1625+1655(x−2)2+(y−45)2=4+1680(x−2)2+(y−45)2=4+5(x−2)2+(y−45)2=9
Identify Radius: Identify the radius of the circle from the standard form equation.The standard form of a circle's equation is (x−h)2+(y−k)2=r2, where (h,k) is the center of the circle and r is the radius.From the equation (x−2)2+(y−45)2=9, we can see that the radius r is the square root of 9, which is 3.
Calculate Diameter: Calculate the diameter of the circle using the radius.The diameter D of a circle is twice the radius, so D=2r.D=2×3=6
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