Further Maths Integration (What's wrong with my method)

I was doing this question and achieved an answer, which is wrong due to using the wrong method (I was tempted to use arcosh but always see hyperbolic substitution on these questions so assumed it was that).
And obviously got a different answer but am still not sure where in my workings I went wrong to actually get an answer. Can anyone help spot my mistake(s)?

Reply 1

Arconik

Reply 2

Interea

You forgot to square the multiplier on cosh(u) when you squared (x+1). You'd need to use a different substitution to get the 4cosh^2(u), which would also then change your value for dx/du.

Reply 3

Arconik

Original post by Interea

You forgot to square the multiplier on cosh(u) when you squared (x+1). You'd need to use a different substitution to get the 4cosh^2(u), which would also then change your value for dx/du.

Ahh I see. Although surely i could just change it to x+1=2coshu. All that will affect is the constant on the outside and it will still work using my method no?

Reply 4

mqb2766

Original post by Arconik

Ahh I see. Although surely i could just change it to x+1=2coshu. All that will affect is the constant on the outside and it will still work using my method no?