What am i doing wrong?

[cerulean yoke]

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[dapper plank]

you made a mistake in the 4th line of your working out. how did you get 2√2 from (2 1/2)^2 ?

[gentle current]

also, you had a negative at the start of the first integral, which was correct, but then you lost it

[gentle current]

going from the first line to the second

it shouldn't be 2^1/2

on the picture, it says $2\frac{1}{2} = \frac{5}{2}$

[runic compass]

Pyrokinetics