SOLUTION: need some help with finding the term that must be added to the expression to create a perfect square trinomial.x2+18x.please help.

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Question 91222: need some help with finding the term that must be added to the expression to create a perfect square trinomial.x2+18x.please help.
Answer by jim_thompson5910(21667) About Me  (Show Source):
You can put this solution on YOUR website!
x%5E2%2B18x Start with the given expression

Take half of the x coefficient 18 to get 9 (ie 18%2F2=9)
Now square 9 to get 81 (ie 9%5E2=81)

Now add 81 to the expression x%5E2%2B18x

x%5E2%2B18x%2B81

So x%5E2%2B18x%2B81 is now a perfect square

Check:

Notice if we factor x%5E2%2B18x%2B81, we get %28x%2B9%29%5E2. So this verifies that x%5E2%2B18x%2B81 is a perfect square.