Answers

2016-07-06T16:01:01+08:00
R^2 + 4r = -1
(r^2+ 4r) = -1
(r^2 + 4r + 4) = -1 + 4
(r^2 + 4r + 4) = 3
(r + 2)^2 = 3
r + 2 = ±√ 3

r +2 = √3
r = √3 -2

r + 2 = -√3
r = -√3 -2


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