What is the equation in standard form of the circle represented by x 2 + y 2 − 10 x − 6 y = 23 ?

X²+y²-10x-6y = 23
(x²-10x)+(y²-6y)=23
We need to complete square for x and y groups.
(x²-2*5x+5²) + (y²- 2*3y+3²)=23 +5² +3²
(x-5)²+(y-3)² = 57  - sometimes this form is called standard
(x-5)²+(y-3)² = (√57)² 
(5,3) is vertex of the circle, and √57 is the radius of the circle.
Sometimes this form called is standard: