Make R the subject (P=10(Q-3R))/(R)

Question

Make R the subject

`(P=10(Q-3R))/(R)`

Answer 1

I must assume that you meant the following:

10(Q-3R)

P = ----------------

R

Multiplying both sides by R, we get PR = 10R(Q-3R), or PR = 10RQ - 30R^2.

Rearranging these terms so that powers of R are in descending order:

30R^2 - 10RQ + PR = 0

Factoring out R, we get

R(30R - 10Q + P) = 0. This has two solutions:

R = 0, and 10Q - P

30R = 10Q - P, so that R = --------------

30