Answer :

To determine the value that should be added to the expression [tex]\( x^2 - 10x + \square \)[/tex] to make it a perfect-square trinomial, we need to follow these steps:

1. Recognize the Form of a Perfect-Square Trinomial: A perfect-square trinomial can be written as [tex]\( (x - a)^2 \)[/tex], which expands to:
[tex]\[ (x - a)^2 = x^2 - 2ax + a^2 \][/tex]

2. Compare with the Given Expression: The given expression is [tex]\( x^2 - 10x + \square \)[/tex]. This expression will match the form [tex]\( x^2 - 2ax + a^2 \)[/tex] where [tex]\( -2a \)[/tex] corresponds to the coefficient of [tex]\( x \)[/tex], which is [tex]\(-10\)[/tex].

3. Solve for [tex]\( a \)[/tex]: Set up the equation based on the comparison:
[tex]\[ -2a = -10 \][/tex]
Solving for [tex]\( a \)[/tex]:
[tex]\[ 2a = 10 \implies a = 5 \][/tex]

4. Find the Missing Term: The missing term that completes the perfect-square trinomial is [tex]\( a^2 \)[/tex]. Calculate [tex]\( a^2 \)[/tex]:
[tex]\[ a^2 = 5^2 = 25 \][/tex]

Therefore, the value that makes the expression [tex]\( x^2 - 10x + \square \)[/tex] a perfect-square trinomial is [tex]\( 25 \)[/tex].

So, the complete perfect-square trinomial is:
[tex]\[ x^2 - 10x + 25 = (x - 5)^2 \][/tex]