It should be said that the score has only a maximum value or a minimum value, because, for example,

Mixed x 2+2x+3 formula

=x^2+2x+ 1+2

=(x+ 1)^2+2

Judging from the result of this formula. This score has a minimum, because (x+ 1) 2 has a minimum, and "+2".

"Don't allow to change.

That is, when x=- 1, it is also the minimum value of this score, which is 2.

No matter what the score is. Just transform according to the idea of complete square, transform a complete square, and add a series of Dongdong numbers to make it equal to the original score.