(Math Quiz 10 – CT) In the expansion ({left( {3x – y} right)^7}), the term containing ({x^4}{y^3}) is:

  • Question:

    In the expansion \({\left( {3x – y} \right)^7}\), the term containing \({x^4}{y^3}\) is:

    Reference explanation:

    Correct answer: A

    The general term in the above expansion is

    \({T_{k + 1}} = C_7^k{.3^{7 – k}}{x^{7 – k}}. {\left( { – 1} \right)^k}. { y^k}\)

    Ask the problem to occur when k = 3 .

    Then the coefficient of the term containing \({x^4}.{y^3}\) is:

    \( – C_7^3{.3^4}. {x^4}. {y^3} = – 2835. {x^4}.y\)


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