Answer:
Explanation:
9 = 3 * 3 = 3²
4x² = 2²x² = (2x)²
9 - 4x² = 3² - (2x)² {a² - b² = (a + b)(a - b) ; a = 3 ; b = 2x}
= (3 +2x)(3 - 2x)
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