Solve for x in the equation x squared minus 12 x plus 36 is equal to 90

Rewrite the left side as a perfect square: x² − 12x + 36 = (x − 6)². Then (x − 6)² = 90, so x − 6 = ±√90 = ±3√10. Therefore x = 6 ± 3√10, which is choice D.

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