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Mathematics · unit version 1

Precalculus: exponential and logarithmic evidence

Identify exponential baselines, construct and fit logarithmic responses, and use transformed inverses with explicit domains. School algebra and graph reading suffice; this is a focused extension, not complete AP preparation.

Open any lesson. Completion records participation; automatic practice checks and human judgment of written arguments are separate. This unit retains its own versioned requirements.

Readiness and preparation

Check your starting point

Try these short questions on paper, then compare your reasoning. They are optional self-checks, not a placement score or a navigation requirement. Use a targeted review when useful and return with your browser’s Back control.

Does a constant output ratio identify an exponential with an unknown vertical shift?

A baseline changes raw ratios, so a shifted model needs a different diagnostic.

Compare reasoning and find a refresher

For equally spaced inputs, y=k+A b^t has a constant ratio after subtracting k. Differences between successive outputs also form a geometric pattern when the model is nonconstant. Raw ratios need not be constant.

Review exponential changes and time units

When is a real logarithm defined?

Inverses and inequalities must preserve the original domain.

Compare reasoning and find a refresher

For log base b of u, require u>0, b>0 and b≠1. A base between zero and one is valid but reverses order. Keep these restrictions when rewriting equations.

Review logarithms and their domains

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Exponential and logarithmic evidence: mixed practice

The mixed assessment has separate response history and review criteria; it does not change lesson participation records.

Lesson sequence

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  1. Identify a shifted exponential from evidence

    Lesson details and objectives

    Use equal-step differences to recover a baseline, then check a prediction in original units.

    • Recover an unknown offset and positive exponential factor from three equally spaced observations under explicit conditions.
    • Diagnose constant, linear, impossible and unequal-step cases before using the difference-ratio formula.
    • Use known asymptotes and nonconsecutive observations, then assess a fresh prediction with its units, domain and uncertainty.

    6 practice tasks.

  2. Construct and validate logarithmic responses

    Lesson details and objectives

    Fit a log-input response and distinguish its original-scale residual evidence from other transformations.

    • Construct a logarithmic response model from transformed input pairs and interpret its domain and coefficients.
    • Execute an actual logarithmic regression and retain coefficients, original-response residuals and unused predictions.
    • Solve input/output targets and explain additive response changes caused by multiplicative input changes.

    7 practice tasks.

  3. Transform inverses without losing domains

    Lesson details and objectives

    Recover full inverse rules and solve inequalities using the correct monotonic direction.

    • Derive and verify both compositions of shifted/scaled exponential inverses with restricted domains.
    • Solve logarithmic inequalities for increasing and decreasing bases while retaining every argument restriction.
    • Explain input dilation, base change, graph direction and asymptote transformations without calculus.

    6 practice tasks.