[tex]3(2b+3)^{2}=36
[/tex] Dividing both sides by 3, we get: [tex](2b+3)^{2}=12[/tex] Taking the square root of each side gives two possibilities: [tex]2b+3= \sqrt{12} =+3 \sqrt{2} \ or\ -3 \sqrt{2} [/tex] From which we get: [tex]b=\frac{-3+3 \sqrt{2} }{2},\ \frac{-3-3 \sqrt{2} }{2}[/tex]