Question 639414
 {{{ 25+9r^4+r^8 = (r^8  + 10r^4 + 25) - r^4 }}}
                = {{{ (r^4 +5)^2 - (r^2)^2}}}
                = {{{ (r^4 + 5 - r^2)(r^4 + 5 + r^2)}}}
                = {{{highlight((r^4 - r^2 + 5)(r^4 + r^2 + 5))}}}