#### Answer

$\sqrt 5$

#### Work Step by Step

$(x_{1},y_{1}) = (0,0)$
$(x_{2},y_{2}) =(-2,1)$
$[d(P_1,P_2)]^{2} = (x_{2}-x_{1})^{2}+(y_{2}-y_{1})^{2} =(-2-0)^{2}+(1-0)^{2}=4+1=5$
$d(P_1,P_2)= \sqrt5$

Published by
Pearson

ISBN 10:
0-32193-104-1

ISBN 13:
978-0-32193-104-7

$\sqrt 5$

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