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Find the positive integer n such that the expansion of (4x - 7y)^n contains a term of the form cx^2*y.

 Dec 30, 2022
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(4x - 7y)^n. 

n cannot be 2, because you will get an xy term, and x^2 term, and a y^2 term with coefficients.

From binomial theorem logic, you can see that cx^a*y^b, where a = b + 1, and a + b = n, a = 2, so we have a + b = 3, and n = 3.

 Dec 31, 2022

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