binomial expansion

what are they asking in part c?

For you to substitute x=1/100 into your expansion then mult through by something and round to 5 dp

I get that bit, but what do they mean: find an approximation to square root of 23?

They’re told you the expansion is equal to (root 23)/5 when x=1/100. Substitute 1/100 into your expansion, put it equal to (root 23)/5 and then rearrange for root 23 ( basically use your expansion to find a value for root 23) xx

When x=1/100 your expansion is approximating sqrt(23)/5

So you can use it to approximate just sqrt(23)