Where a and b are real numbers, and c can be complex, this equation is the most basic form of the quadratic equation.
x = (-b ± √(b^2 - 4ac)) / 2a
x = (-4 + √(-4 - 4)) / 2(2)
x = (-(-5) ± √((-5)^2 - 4(2)(2))) / 2(2)
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