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    IB Math AASL
    /
    Sequences & Series
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    Video

    Video Reviews

    Watch comprehensive video reviews for most units, designed for final exam preparation. Each video includes integrated problems you can solve alongside detailed solutions.

    Not your average video:

    Interactive Problems: Solve problems alongside the video with step-by-step guidance and detailed solutions.

    Exam Preparation: Complete unit reviews designed for final exam preparation with all key concepts covered systematically.

    Expert Teaching: High-quality instruction from Perplex co-founder James Mullen with clear explanations, worked examples, and exam tips.

    Not your average video:

    Interactive Problems: Solve problems alongside the video with step-by-step guidance and detailed solutions.

    Exam Preparation: Complete unit reviews designed for final exam preparation with all key concepts covered systematically.

    Expert Teaching: High-quality instruction from Perplex co-founder James Mullen with clear explanations, worked examples, and exam tips.

    Sequences & Series

    Video Reviews

    Watch comprehensive video reviews for Sequences & Series, designed for final exam preparation. Each video includes integrated problems you can solve alongside detailed solutions.

    Not your average video:

    Interactive Problems: Solve problems alongside the video with step-by-step guidance and detailed solutions.

    Exam Preparation: Complete unit reviews designed for final exam preparation with all key concepts covered systematically.

    Expert Teaching: High-quality instruction from Perplex co-founder James Mullen with clear explanations, worked examples, and exam tips.

    Not your average video:

    Interactive Problems: Solve problems alongside the video with step-by-step guidance and detailed solutions.

    Exam Preparation: Complete unit reviews designed for final exam preparation with all key concepts covered systematically.

    Expert Teaching: High-quality instruction from Perplex co-founder James Mullen with clear explanations, worked examples, and exam tips.

    SequencesSeriesPaper 1 ProblemsFinancePaper 2 Problems

    The video will automatically pause when it reaches a problem.

    Identifying Geometric Sequences

    SL Core 1.3

    A sequence is geometric if the ratio between consecutive terms is always constant, ie

    un​un+1​​=ris constant for all n∈N🚫

    We call r the common ratio.

    For instance, the sequence

    8,2,21​,81​…

    is geometric with r=41​, but

    3,6,9,12…

    is not since 69​=23​=2=36​.


    Example

    For what value(s) of k is the sequence 2, (k−1),8… geometric?


    The sequence is geometric if

    k−18​=2k−1​

    Cross multiplying:

    2⋅8=(k−1)2=k2−2k+1


    Simplifying:

    k2−2k−15=0

    Factoring

    (k−5)(k+3)=0

    So k=5 or k=−3.

    Identifying Geometric Sequences

    SL Core 1.3

    A sequence is geometric if the ratio between consecutive terms is always constant, ie

    un​un+1​​=ris constant for all n∈N🚫

    We call r the common ratio.

    For instance, the sequence

    8,2,21​,81​…

    is geometric with r=41​, but

    3,6,9,12…

    is not since 69​=23​=2=36​.


    Example

    For what value(s) of k is the sequence 2, (k−1),8… geometric?


    The sequence is geometric if

    k−18​=2k−1​

    Cross multiplying:

    2⋅8=(k−1)2=k2−2k+1


    Simplifying:

    k2−2k−15=0

    Factoring

    (k−5)(k+3)=0

    So k=5 or k=−3.

    SequencesSeriesPaper 1 ProblemsFinancePaper 2 Problems