Question 901187
There are many ways to do this.  I did it the easiest way for me.
Take the square root of 89.  It's closest to 9.  That's your middle number.
7,9,11 is the sequence.<br>
Prove it:<i>the sum of the squares of the first and third is 89 more than the square of the second.</i>
{{{7^2}}}+{{{11^2}}}={{{9^2}}}+89
49 + 121 = 81 + 89
170 = 170