I came across this funny proof-
$$4$$
$$=4+\frac 92-\frac 92$$
$$=\sqrt{(4-\frac 92)^2}+\frac 92$$
$$=\sqrt{16+\frac{81}{4}-36}+\frac 92$$
$$=\sqrt{25+\frac {81}{4}-45}+\frac 92$$
$$=\sqrt{(5-\frac 92)^2}+\frac 92$$
$$=5-\frac 92+\frac 92$$
$$=5$$
I suspect,that the error is in the second line where operation on negative is done before positive violating $BODMAS$ rule.But,$\sqrt{(4-\frac 92)^2}=4-\frac 92$ and the similar solving continues.So, where is the real error?
Thanks for any help!!