Question

$(3m - n)2 - (m - 2n)2$
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Answer 1

Step-by-step explanation:

(3m - n )² - (m - 2n)²

Take first term

(3m)² - 2(3m)(n) + (n)²

9m² - 6mn + n²

Now second term

m² + 2(m)(2n) - (2n)²

= m² + 4mn - 4n²

3m² -6mn + n² + m² + 4mn - 4n²

= 4m² - 2mn - 3n²

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