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3x^{2}=7\times 4
Multiply both sides by 4.
3x^{2}=28
Multiply 7 and 4 to get 28.
x^{2}=\frac{28}{3}
Divide both sides by 3.
x=\frac{2\sqrt{21}}{3} x=-\frac{2\sqrt{21}}{3}
Take the square root of both sides of the equation.
3x^{2}=7\times 4
Multiply both sides by 4.
3x^{2}=28
Multiply 7 and 4 to get 28.
3x^{2}-28=0
Subtract 28 from both sides.
x=\frac{0±\sqrt{0^{2}-4\times 3\left(-28\right)}}{2\times 3}
This equation is in standard form: ax^{2}+bx+c=0. Substitute 3 for a, 0 for b, and -28 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.
x=\frac{0±\sqrt{-4\times 3\left(-28\right)}}{2\times 3}
Square 0.
x=\frac{0±\sqrt{-12\left(-28\right)}}{2\times 3}
Multiply -4 times 3.
x=\frac{0±\sqrt{336}}{2\times 3}
Multiply -12 times -28.
x=\frac{0±4\sqrt{21}}{2\times 3}
Take the square root of 336.
x=\frac{0±4\sqrt{21}}{6}
Multiply 2 times 3.
x=\frac{2\sqrt{21}}{3}
Now solve the equation x=\frac{0±4\sqrt{21}}{6} when ± is plus.
x=-\frac{2\sqrt{21}}{3}
Now solve the equation x=\frac{0±4\sqrt{21}}{6} when ± is minus.
x=\frac{2\sqrt{21}}{3} x=-\frac{2\sqrt{21}}{3}
The equation is now solved.