Write $x^2 - 10x + 16$ in the form $(x + a)^2 + b.$ - OCR - GCSE Maths - Question 16 - 2017 - Paper 1

To rewrite the expression in the form $(x + a)^2 + b$, we start with the quadratic expression.

1. Identify the coefficient of $x$: here, it is $-10$.
2. Take half of this coefficient, which is $-5$, and square it: $ext{Half of } -10 = -5 ext{ and } (-5)^2 = 25.$
3. Rewrite the quadratic by adding and subtracting this square:
   $x^2 - 10x + 25 - 25 + 16 = (x - 5)^2 - 9.$
4. Therefore, the expression can be rewritten as: $(x - 5)^2 - 9.$