Easy way to square a number if you know another one

Let say you know 12 squared but you want to figure out 14 squared.  This way I will show is more complex looking but uses simple math.  Here is the formula: y(2)=y squared

y(2)=(y+x)(y-x) + x(2)

Here are some examples:

7(2)=(7+5)(7-5)+5(2)

7(2)=(12)(2)+25

7(2)=24+25

7(2)=49

14(2)=(14+12)(14-12) + 12(2)

14(2)=(26)(2)+144

14(2)=52+144

14(2)=196