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## Homework Statement

Observer O sees a red flash of light at the origin at t=0 and a blue flash of light at x = 3.26km at a time t = 7.63 [tex]\mu[/tex] seconds. What are the distance and the time interval between the flasheds according to ovserver O', who moes relative to O in the direction of increasing x with a speed of 0.625c? Assume that the origins of the two coordinate systems line up at t = t' = 0.

## Homework Equations

x' = [tex]\gamma[/tex](x - ut)

t' = [tex]\gamma[/tex]t - (u/c^2)x

## The Attempt at a Solution

I solved for t' and got the answer 1.73 [tex]\mu[/tex]seconds. From the back of my textbook, this seems to be the correct answer.

When I put x = 3.26km into the first equation above, I always get the answer to be 2.34 km. The answer fromt the back of my textbook says [tex]\Delta[/tex] x' = -1.90 km.

I'm wondering what i'm doing wrong...