complete the square
x² - 8x + 10
to complete square we have to add a number
this number u get from halving coefficient on x and then squaring that quotient.
divide -8 by 2 to get -4. square that to get 16
so we need to add n subtract 16
x² - 8x +16 - 16 + 10
x² - 8x +16 factors into (x-4)²
= (x-4)² - 16 + 10
= (x-4)² - 6