Answer:
2
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
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