21.已知直线l1:tx+y+t+1=0l_{1}:tx+y+t+1=0l1:tx+y+t+1=0与直线l2:x−ty+t−1=0l_{2}:x-ty+t-1=0l2:x−ty+t−1=0相交于点PPP,动点AAA,BBB在圆C:x2+y2−14x+2y+47=0C:x^{2}+y^{2}-14x+2y+47=0C:x2+y2−14x+2y+47=0上,且∣AB∣=2\vert AB\vert =2∣AB∣=2,则∣PA→+PB→∣\vert \overrightarrow{PA}+\overrightarrow{PB}\vert∣PA+PB∣的取值范围是 ___[62,142][6\sqrt{2},14\sqrt{2}][62,142]___.