Dimitri is solving the equation x^2 – 10x = 21. Which value must be added to both sides of the equation to make the left side a perfect-square trinomial?
a. 0
b. 4
c. 25
d. 100
we are given the expression x 2 - 10x = 21 where a number is to be added in both sides to complete the equation by completing the square. In this case, (-10/2)^2 is equal to 25. The number that is added in the left side of the equation is equal then to 25.
