can you help me CAS this?

[VCAA Official]

The equation: 3-^x -e^-x =0 is a semi circle.

to find the value of a, the x value of the intercept with the x axis on the positive side of this equation, we can use the cas calculator.

this will give us the result of:

in(((+/-)(squartroot5 - 3)/2)

the value of a will be the positive value since the other value is the negative one. i think we can assume that the negative of the +/- in the negative a value so we can put it so far as:

in(((+/-)(squartroot5 - 3)/2)

Now. the solutions say the answer is:

in((3+squareroot5)/2).

I don't know what steps they used to go from my answer to the book answer. could you please explain this to me?

thank you.

[roberto]

what do youmean by "in"?

[chopz]

 do you mean ln? loge?

[VCAA Official]

yep I did
sorry for my mistake!

[roberto]

and how bout 3-^x     ? in the first line?? not sure wat that means either?