is the same as where is half of
Find half of +6 (call this p)
Factorise -2 out of the first two terms only
Use square-shaped brackets
Complete the square on the x^{2} - 4x inside the brackets (write in the form (x + p)^{2} - p^{2} where p is half of -4)
Simplify the numbers inside the brackets
(-2)^{2} is 4
Multiply -3 by all the terms inside the square-shaped brackets
Simplify the numbers
This is now in the form a(x + p)^{2} + q where a = -3, p = -2 and q = 36