SOLUTION: 1/R = 1/r1 + 1/r2 for R but i don't wanna take L.C.M plz help

Algebra ->  Expressions-with-variables -> SOLUTION: 1/R = 1/r1 + 1/r2 for R but i don't wanna take L.C.M plz help      Log On


   

Question 1147924: 1/R = 1/r1 + 1/r2 for R
but i don't wanna take L.C.M
plz help
Found 2 solutions by josgarithmetic, ikleyn:
Answer by josgarithmetic(39621) About Me  (Show Source):
You can put this solution on YOUR website!
Unclear.
system%28r%5E1%2Cand%2Cr%5E2%29
OR
system%28r%5B1%5D%2Cand%2Cr%5B2%5D%29
?

Answer by ikleyn(52824) About Me  (Show Source):
You can put this solution on YOUR website!
.

Given


    1%2FR = 1%2Fr%5B1%5D + 1%2Fr%5B2%5D.


Then


    1%2FR = r%5B2%5D%2F%28r%5B1%5D%2Ar%5B2%5D%29 + r%5B1%5D%2F%28r%5B1%5D%2Ar%5B2%5D%29 = %28r%5B1%5D%2Br%5B2%5D%29%2F%28r%5B1%5D%2Ar%5B2%5D%29.


Hence,


    R = %28r%5B1%5D%2Ar%5B2%5D%29%2F%28r%5B1%5D%2Br%5B2%5D%29.    ANSWER

Solved.