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Solve for x (complex solution)
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28xx=-67.2
Variable x cannot be equal to 0 since division by zero is not defined. Multiply both sides of the equation by x.
28x^{2}=-67.2
Multiply x and x to get x^{2}.
x^{2}=\frac{-67.2}{28}
Divide both sides by 28.
x^{2}=\frac{-672}{280}
Expand \frac{-67.2}{28} by multiplying both numerator and the denominator by 10.
x^{2}=-\frac{12}{5}
Reduce the fraction \frac{-672}{280} to lowest terms by extracting and canceling out 56.
x=\frac{2\sqrt{15}i}{5} x=-\frac{2\sqrt{15}i}{5}
The equation is now solved.
28xx=-67.2
Variable x cannot be equal to 0 since division by zero is not defined. Multiply both sides of the equation by x.
28x^{2}=-67.2
Multiply x and x to get x^{2}.
28x^{2}+67.2=0
Add 67.2 to both sides.
x=\frac{0±\sqrt{0^{2}-4\times 28\times 67.2}}{2\times 28}
This equation is in standard form: ax^{2}+bx+c=0. Substitute 28 for a, 0 for b, and 67.2 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.
x=\frac{0±\sqrt{-4\times 28\times 67.2}}{2\times 28}
Square 0.
x=\frac{0±\sqrt{-112\times 67.2}}{2\times 28}
Multiply -4 times 28.
x=\frac{0±\sqrt{-7526.4}}{2\times 28}
Multiply -112 times 67.2.
x=\frac{0±\frac{112\sqrt{15}i}{5}}{2\times 28}
Take the square root of -7526.4.
x=\frac{0±\frac{112\sqrt{15}i}{5}}{56}
Multiply 2 times 28.
x=\frac{2\sqrt{15}i}{5}
Now solve the equation x=\frac{0±\frac{112\sqrt{15}i}{5}}{56} when ± is plus.
x=-\frac{2\sqrt{15}i}{5}
Now solve the equation x=\frac{0±\frac{112\sqrt{15}i}{5}}{56} when ± is minus.
x=\frac{2\sqrt{15}i}{5} x=-\frac{2\sqrt{15}i}{5}
The equation is now solved.