.
f(x) = 2x^2 - 8x + 11 = 2*(x^2 - 4x) + 11 = 2*(x^2 - 2*2*x + 2^2) - 2*2^2 + 11 =
= 2*(x-2)^2 + 3.
Done.
--------------
To see many other similar problem solved by the "completing the square" method and to learn the subject, look into the lesson
- HOW TO complete the square - Learning by examples
in this site.