I am working on a long problem and the solution i am getting differs from the answer in the textbook.
It boils down to completing the square. The method i use works in the first half of the problem but the book gets a different answer in the 2nd half. Basically for the coordinates of the centre of a circle my x coordinate is correct, but my y coordinate is incorrect.
Can somebody complete the square on the following and give me coordinates for the centre of the circle. My answer is (x=0.5, y=-0.5). The book gives the y as -1.
The expression is: 4x^2+4y^2-4x+8y-11=0.
My solution has : y^2+2y becomes y^2+y+0.25 (b=0.5)= (y+0.5)^2-0.25
The book has: y^2+2y becomes (y+1)^2-1