Physics Energy Maths simplifying

Question

   

 

 

How does the second line simplify to the third like R_Eh seems to disappear

Answer 1

Hi Ian.  I am guessing, in this case, that h is considered to be much less than r_E.  In that case, if you add r_E and h, the result is effectively equal to just r_E (which is why the "equals" sign is replaced with an "approximately equal" sign).  So r_E(r_E+h) is, with that assumption, just r_E * r_E = r_E².