If the equation of a circle is the square of X, the square of Y, KX 2Y, and the square of k = 0, then the coordinates of the center of a circle are formula x^2+y^2+kx+2y+k^2＝0 (x+k/2)^2+(y+1)^2=1-(3/4)k^2 The circle has the largest area That is, the maximum radius That is, 1 - (3 / 4) k ^ 2 is the largest Then k = 0 Center (0, - 1) radius 1 X ^ 2 + (y + 1) ^ 2 = 1 1 - (3 / 4) k ^ 2 max Then how can we get k = 0

If the equation of a circle is the square of X, the square of Y, KX 2Y, and the square of k = 0, then the coordinates of the center of a circle are formula x^2+y^2+kx+2y+k^2＝0 (x+k/2)^2+(y+1)^2=1-(3/4)k^2 The circle has the largest area That is, the maximum radius That is, 1 - (3 / 4) k ^ 2 is the largest Then k = 0 Center (0, - 1) radius 1 X ^ 2 + (y + 1) ^ 2 = 1 1 - (3 / 4) k ^ 2 max Then how can we get k = 0

Y = 1 - (3 / 4) k ^ 2 is regarded as a quadratic function, the opening is downward, and the symmetry axis is Y axis
When k = 0, y has a maximum value of 1