Question

20/r + 12/r-4 = 4

Answer 1

\(\frac{20(r-4)}{r(r-4)}+\frac{12r}{r(r-4)}=4\)
\(\frac{32r-80}{r(r-4)}=4\)
\(32r-80=4r(r-4)\)
\(32r-80=4r^2-16r\)
\(8r-20=r^2-4r\)
\(r^2-12r+20=0\)
\((r-2)(r-10)=0\)
\(=2\) or \(r=10\).