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12=3\left(3a^{2}+2\right)
Multiply both sides of the equation by 3a^{2}+2.
12=9a^{2}+6
Use the distributive property to multiply 3 by 3a^{2}+2.
9a^{2}+6=12
Swap sides so that all variable terms are on the left hand side.
9a^{2}=12-6
Subtract 6 from both sides.
9a^{2}=6
Subtract 6 from 12 to get 6.
a^{2}=\frac{6}{9}
Divide both sides by 9.
a^{2}=\frac{2}{3}
Reduce the fraction \frac{6}{9} to lowest terms by extracting and canceling out 3.
a=\frac{\sqrt{6}}{3} a=-\frac{\sqrt{6}}{3}
Take the square root of both sides of the equation.
12=3\left(3a^{2}+2\right)
Multiply both sides of the equation by 3a^{2}+2.
12=9a^{2}+6
Use the distributive property to multiply 3 by 3a^{2}+2.
9a^{2}+6=12
Swap sides so that all variable terms are on the left hand side.
9a^{2}+6-12=0
Subtract 12 from both sides.
9a^{2}-6=0
Subtract 12 from 6 to get -6.
a=\frac{0±\sqrt{0^{2}-4\times 9\left(-6\right)}}{2\times 9}
This equation is in standard form: ax^{2}+bx+c=0. Substitute 9 for a, 0 for b, and -6 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.
a=\frac{0±\sqrt{-4\times 9\left(-6\right)}}{2\times 9}
Square 0.
a=\frac{0±\sqrt{-36\left(-6\right)}}{2\times 9}
Multiply -4 times 9.
a=\frac{0±\sqrt{216}}{2\times 9}
Multiply -36 times -6.
a=\frac{0±6\sqrt{6}}{2\times 9}
Take the square root of 216.
a=\frac{0±6\sqrt{6}}{18}
Multiply 2 times 9.
a=\frac{\sqrt{6}}{3}
Now solve the equation a=\frac{0±6\sqrt{6}}{18} when ± is plus.
a=-\frac{\sqrt{6}}{3}
Now solve the equation a=\frac{0±6\sqrt{6}}{18} when ± is minus.
a=\frac{\sqrt{6}}{3} a=-\frac{\sqrt{6}}{3}
The equation is now solved.