What number should be added to both sides of the equation to complete the square in x^2 +8x=17

Hey there! :)
The formula for (a + b)^2 is a^2 + 2ab + b^2. In this case, x is a, and so b would have to be 4. We would need to add 4^2 = 16 to both sides of the equation to complete the square.
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Hope this helps!
==jding713==