90/(v-3) - 90/(v+3) = 0.5
90(v+3) - 90(v-3) = 0.5(v*v - 9)
270 + 270 = 0.5v*v - 4.5
540 = 0.5v*v - 4.5
1080 = v*v - 9
v*v = 1089
v = 33 (since speed cannot be negative)
90/(v+3) = 2.5
ques.
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