Fill in the blank with the correct response.

If x is a whole number and 437 = (21 + x) (21 - x), then x = ?

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Step-by-step explanation:

437 = (21 + x) (21 - x)

(21 + x) (21 - x) = 437 { (a + b) (a - b) = a² - b²}

21² - x² = 437

441 - x² = 437 {subtract 441 from both sides}

-x² = 437 - 441

-x² = - 4 {Divide both sides by [-1] }

x² = 4

x² = 2²

x = 2