Final answer:
To make the expression x² + x a perfect-square trinomial, you need to add 0.25.
Step-by-step explanation:
To make the expression x² + x a perfect-square trinomial, you need to find the missing value that, when added, will allow the expression to be factored into the square of a binomial. The coefficient of the x term in the expression is 1, so you can take half of this coefficient (1/2) and square it to find the value you need to add. Half of 1 is 0.5, and when you square it, you get 0.25. Therefore, the value you must add to the expression is 0.25 to make it a perfect-square trinomial.
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