## Elementary Geometry for College Students (5th Edition)

$d = 2 \sqrt {(c - a)^{2} + (d - b)^{2}}$
$d = \sqrt {(2c - 2a)^{2} + (2d - 2b)^{2}}$ $d = \sqrt {(2(c - a))^{2} + (2(d - b))^{2}}$ $d = \sqrt {4(c - a)^{2} + 4(d - b)^{2}}$ $d = \sqrt {4((c - a)^{2} + (d - b)^{2})}$ $d = 2 \sqrt {(c - a)^{2} + (d - b)^{2}}$