What number should be added to the expression x2+10x to change it into a perfect square trinomial?
To change the expression x^2 + 10x into a perfect square trinomial, we need to add half of the middle term squared.
In this case, half of the middle term is 10/2 = 5.
5 squared is 25.
Therefore, we need to add 25 to the expression x^2 + 10x to make it a perfect square trinomial.
So, the number that should be added is 25.
The expression becomes x^2 + 10x + 25 = (x + 5)^2.