Answer :
distance = sqrt (x2 - x1)^2 + (y2 - y1)^2
(0,6)....x1 = 0 and y1 = 6
(0,-2)...x2 = 0 and y2 = -2
now we sub
d = sqrt (0 - 0)^2 + (-2 - 6)^2
d = sqrt (0^2 + (-8^2)
d = sqrt (0 + 64)
d = sqrt 64
d = 8 <====
(0,6)....x1 = 0 and y1 = 6
(0,-2)...x2 = 0 and y2 = -2
now we sub
d = sqrt (0 - 0)^2 + (-2 - 6)^2
d = sqrt (0^2 + (-8^2)
d = sqrt (0 + 64)
d = sqrt 64
d = 8 <====