## § Sum of quadratic errors

- Consider the function $(x - a)^2 + (x - b)^2$
- Minimum error is at $2(x - a) + 2(x - b)$, or at
`(a + b)/2`

. - As we move away towards either end-point, the
*error always increases *! - So the "reduction in error" by moving towards
`b`

from `(a + b)/2`

is ALWAYS DOMINATED by the "increase in error" by moving towards `a`

from `(a + b)/2`

.