Question 1127650
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The  "blank number"  is  "1".




If you are a real student and If you really want to learn on completing the squares method,  then look into the lesson

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/quadratic/lessons/Learning-by-examples-on-HOW-TO-complete-the-square.lesson>HOW TO complete the square - Learning by examples</A> 

in this site.


Learn the subject from there once and for all.



It is ELEMENTARY . . .