A radar station at point A is tracking two ships. Ship B is 4.5 km away in a direction 42degrees east of north. Ship C is 3.3 km away in a direction 58degrees west of north. How far apart are the two ships, to the nearest tenth of a kilometre?

First step is to get rid of the square root. remember that a square root is the same as raising to the (1/2) power. see below: multiply exponents per exponent rules to get: remember you subtract exponents from the denominator and add exponents in the numerator so: simplify further: so a is the correct choice. if you don't understand this google exponent rules and it will you understand. look at the image results.

Difference means subtraction