I made a formula in LibreOffice Writer with Insert > Object > Formula…
This is my source code:
{ sum from{i=1}to{8} (x_i - bar x )(y_i - bar y)} over
{ sqrt{sum from{i=1} to{8} (x_i - bar x)^2 }sqrt{sum from{i=1} to{8} (y_i - bar y)^2 } }
Did I do something wrong?