College Algebra / Alg 190 · Atom · ~20 seconds
Square Roots of Negative Numbers
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State
The principal square root of a negative number is imaginary: √(−a) = i√a for positive a.
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√(−9) = 3i, and the check squares back: (3i)² = 9i² = −9. The radical now answers every real input.
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Factor the −1 out as i before touching anything else.
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