Binomial Theorem (DP IB Analysis & Approaches (AA))

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  • What is the binomial theorem?

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  • What is the binomial theorem?

    The binomial theorem is a method for expanding a two-term expression in a bracket raised to a power, e.g. open parentheses a plus b close parentheses to the power of n.

  • True or False?

    The binomial theorem only applies to linear expressions.

    False.

    The binomial theorem applies to any two-term expression, but in IB it is most often applied to linear expressions.

  • State the equation for the binomial theorem.

    The equation for the binomial theorem is open parentheses a plus b close parentheses to the power of n equals a to the power of n plus scriptbase straight C subscript 1 end scriptbase presubscript blank presuperscript n space a to the power of n italic minus italic 1 end exponent b plus... plus scriptbase straight C subscript r end scriptbase presubscript blank presuperscript n space a to the power of n minus r end exponent b to the power of r plus... plus b to the power of n

    Where:

    • scriptbase straight C subscript r end scriptbase presubscript blank presuperscript n equals fraction numerator n factorial over denominator r factorial open parentheses n minus r close parentheses factorial end fraction

    This equation is valid for any n element of straight natural numbers (i.e., n equals 0 comma space 1 comma space 2 comma space 3 comma space...).

    The equation is in the exam formula booklet.

  • What is the binomial coefficient?

    The binomial coefficient scriptbase straight C subscript r end scriptbase presubscript blank presuperscript n is used to find the coefficients in a binomial expansion.

    Its value is given by scriptbase straight C subscript r end scriptbase presubscript blank presuperscript n equals fraction numerator n factorial over denominator r factorial open parentheses n minus r close parentheses factorial end fraction, which is in the exam formula booklet (although you will usually use your GDC to find the value of the coefficients in an expansion).

    scriptbase straight C subscript r end scriptbase presubscript blank presuperscript n also represents the number of ways to choose r items out of n different items.

  • True or False?

    Binomial coefficients are always integers.

    True.

    Binomial coefficients are always integers.

  • True or False?

    Pascal's triangle can be used to find binomial coefficients scriptbase straight C subscript r end scriptbase presubscript blank presuperscript n.

    True.

    Pascal's triangle is a triangular array of the binomial coefficients, and can be used to find scriptbase straight C subscript r end scriptbase presubscript blank presuperscript n for different values of n and r.

    However Pascal's triangle becomes awkward to use when n gets large.

  • True or False?

    In Pascal's triangle, each number is the sum of the two numbers directly above it.

    True.

    In Pascal's triangle, each number is the sum of the two numbers directly above it.

  • True or False?

    scriptbase straight C subscript r end scriptbase presubscript blank presuperscript n equals scriptbase straight C subscript n minus r end subscript end scriptbase presubscript blank presuperscript n

    True.

    scriptbase straight C subscript r end scriptbase presubscript blank presuperscript n equals scriptbase straight C subscript n minus r end subscript end scriptbase presubscript blank presuperscript n

    E.g. scriptbase straight C subscript 2 end scriptbase presubscript blank presuperscript 7 equals scriptbase straight C subscript 5 end scriptbase presubscript blank presuperscript 7

  • What does the ellipsis (...) indicate in a binomial expansion?

    The ellipsis (...) in a binomial expansion indicates that the expansion continues.

  • What does 'in ascending powers' mean?

    'In ascending powers' means that the terms are arranged so that the power of the variable increases with each term.