（2√2-r）²=r²+1化简，得8-4√2r+r²=r²+1移项得：-4√2r+r²-r²=1-8合并同类项得：-4√2r=-7系数化为1得：r=7/4√2，分子分母同时乘以√2，即r=7√2/8
(2√2-r)^2=r^2+1解：8-(4√2)r+r^2=r^2+1移项得：-(4√2)r+r^2-r^2=1-8合并同类项得：-(4√2)r=-7系数化为1得：r=7/(4√2)即r=(7√2)/4。
