Complete the square and write the equation in standard form. Then give the center and radius of the circle.
x2+y2-14x-2y+50=4
by 
stella
ANSWERS: 2
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centre is (7,-1) radius is 2 units equation is (x-7)^2 + (y+1)^2 = 4
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I guess you don't know how to do it. Look at the expansion formula (a+b)^2=a^2+2ab+b^2. You see that it is comprised of the square of the first number, then the double product of goth numbers and then the square of the second number (obviously, the order of the terms does not matter). In you original equation you bring together all the terms containing x. You see x^2. To complete the square you need the double product term. You have 14x; since x is the first number, -14 must be twice the second number, so the second number is -7. Its square is 49, which gives you altogether (x-7)^2. You borrow 49 from 50 in the original equation, which leaves you with (x-7)^2+1 <this is what remains when you take the needed 49 from the original 50>+(y^2-2y). Now you treat the y terms similarly: -2y is the double product so the second number in the full square is -1. Its square is 1, and this is exactly what you have remaining from the original 50, so finally you get (x-7)^2+(y-1)^2.
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