under the same denominator r(r-4)
[6(r-4)] / (r(r-4)) + (4r) / (r(r-4)) = 1
(6r - 24 + 4r) / (r(r-4)) = 1
10r - 24 = r (r-4)
10r - 24 = r² - 4r
r² - 14r + 24 = 0
Δ = (-14)² - 4*1*24 = 100 = 10²
x' = (14 + 10) / 2 = 12
x" = (14 - 10) / 2 = 2
i'm french - so I answered as we learn in France :)
