Question 1100243
.
<pre>
Let x be the unknown length of the original square.


Then you have this equation


{{{(x+1)^2 - x^2}}} = b.


Simplify and solve for x:


{{{x^2 + 2x + 1 - x^2}}} = b,

2x + 1 = b.


x = {{{(b-1)/2}}}.
</pre>

Solved.