A sector has perimeter 18 cm and area 20 cm2^22. Its radius is r r\,r cm and its angle is θ \theta\,θ radians.
Show that r r\,r satisfies r2−9r+20=0r^2-9r+20=0r2−9r+20=0.
Find the two possible pairs (r,θ)(r,\theta)(r,θ).