Dimitri is solving the equation x2 – 10x = 21. which value must be added to both sides of the equation to make the left side a perfect-square trinomial? 0 4 25 100

25

Step-by-step explanation:

The value you add to both sides is found by taking half the linear term, squaring it, and adding it to both sides.  Our linear term here is 10 (the negative doesn't matter).  Half of 10 is 5, and 5 squared is 25.  So the value you add to both sides to make this a perfect square binomial is 25.

36 is the final answer! : )