+129899 Rewrite as
10r^2 + 68r = 45 divide through by 10
r^2 + (68/10)r = 45/10
r^2 + 6.8r = 4.5 take 1/2 of 6.8 = 3.4 square it = 11.56 add to both sides
{ the number in red is what we need later }
r^2 + 6.8r + 11.56 = 4.5 + 11.56
(r + 3.4)^2 = 16.06 take both roots
r + 3.4 = ±√ 16.06
r = √16.06 - 3.4 ≈ .6075
or
r = - √16.06 - 3.4 ≈ -7.4075
