How do you solve #9r ^ { 2} + 9r - 1= 0#?

1 Answer
May 7, 2017

See below.

Explanation:

This is unfactorable (unfortunately), so we must apply the quadratic formula.

#9r ^ { 2} + 9r - 1= 0#

#r=\frac(-9\pmsqrt(9^2-4(9)(-1)))(18)=\frac(-9\pmsqrt(81+36))(18)#

#r=\frac(-9\pmsqrt(117))(18)=\frac(-9\pmsqrt(3^2*13))(18)=\frac(-9\pm3sqrt(13))(18)=\frac(-3\pmsqrt(13))(6)#