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2x^{2}=72-4
Subtract 4 from both sides.
2x^{2}=68
Subtract 4 from 72 to get 68.
x^{2}=\frac{68}{2}
Divide both sides by 2.
x^{2}=34
Divide 68 by 2 to get 34.
x=\sqrt{34} x=-\sqrt{34}
Take the square root of both sides of the equation.
2x^{2}+4-72=0
Subtract 72 from both sides.
2x^{2}-68=0
Subtract 72 from 4 to get -68.
x=\frac{0±\sqrt{0^{2}-4\times 2\left(-68\right)}}{2\times 2}
This equation is in standard form: ax^{2}+bx+c=0. Substitute 2 for a, 0 for b, and -68 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.
x=\frac{0±\sqrt{-4\times 2\left(-68\right)}}{2\times 2}
Square 0.
x=\frac{0±\sqrt{-8\left(-68\right)}}{2\times 2}
Multiply -4 times 2.
x=\frac{0±\sqrt{544}}{2\times 2}
Multiply -8 times -68.
x=\frac{0±4\sqrt{34}}{2\times 2}
Take the square root of 544.
x=\frac{0±4\sqrt{34}}{4}
Multiply 2 times 2.
x=\sqrt{34}
Now solve the equation x=\frac{0±4\sqrt{34}}{4} when ± is plus.
x=-\sqrt{34}
Now solve the equation x=\frac{0±4\sqrt{34}}{4} when ± is minus.
x=\sqrt{34} x=-\sqrt{34}
The equation is now solved.