The given expression is [tex] x^{2} -20x =10 [/tex]
This is of the form [tex] ax^{2} +bx=c [/tex]
Comparing the equations a=1,b=-20 and c=10.
To complete the square we take half then coefficient of x that is b and square it .This is added to both sides of the equation.
The coefficient of x is 20 .Half of it is 10 .Square of 10 is 100.
[tex] \frac{b}{2a} =\frac{-20}{2}= -10 [/tex]
[tex] (-10)^{2} =100 [/tex]
This 100 is added to both sides.The equation becomes:[tex] x^{2} -20x +100=20+100 [/tex]
Or [tex] x^{2} -20x+100 =110 [/tex]
