Question 1313
2/(r2-r) - 1 = 2(r-1)

2/r(r-1) - 1 = 2/(r-1)

Multiply the above eqn by r(r-1)

2 - r(r-1) = 2r
2 - r2 + r = 2r
2 - r2 + r - 2r = 0
2 - 2r + r - r2 = 0
2(1-r) + r(1-r) = 0
(1-r)(2+r) = 0
1-r = 0 -> r = 1 (not feasible)
2+r = 0 -> r = -2

Therefore r = -2