COMPLETE THE SQUARE
X^2-10X+27
do you know what a "perfect square trinomial" is?
NO
ok so a perfect square trinomial, so-called is really just a binomial of second degree that is \(\bf (a\pm b)^2\) now keep in mind that \(\bf (a\pm b)^2 = a^2\pm 2ab+b^2\)
ok
the plus/minus is not required since the terms are general to begin with
so as an example if I had say \(\bf 4x^2+ 12xy + 9y^2\) is really equals to \(\bf (2x)^2 + 2(2x)(3y) + (3y)^2 \implies (2x+3y)^2\)
$$\bf x^2-10x+27\\ \text{let's group the "x" first}\\ (x^2-10x)+27\\ \text{let's make them a perfect square trinomial}\\ (x^2-10x+\square?)+27 $$ so, what number do you think we need there for a perfect square trinomial? that is what number there multiplied by 2 will give me "10", the middle term
$$\bf ((x^2-10x)+27\\ (x^2-2(\square?x)+\square?^2)+27\\ $$
so, we just need that one number
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