Abc is a right triangle if ab= 3 and ac= 7 find bc leave your answer in simplest radical form

If you have a right triangle and the side AC is the hypotenuse (the longest side) then your equation would be a^2+b^2=c^2 like mentioned before. but you have to put the numbers in the correct spot. 

a in the equation= side ab, b in the equation= side bc, and c in the equation= side as 

so.. 

3^2+b^2=7^2 
9+b^2=49 
b^2=40 
b= the square root of 40 or 
2 square roots of 10 (2 then square root sign with 10 in the square root) which would probably be the simplest form.