So far, so good. But:
For the second one: " a/ sq.rt40/2"
For the last one: "2/ 1+sq.rt6"
We need to multiply the top and bottom by the "conjugate." (The works on the ones above too.) It works like this:
which no has no square root in the final expression.
Thus if we have a denominator with a in it we multiply the top and bottom by , which is called the conjugate of .