Precalculus: constructing and validating polynomial models
Build constrained cubic and quartic models, then distinguish interpolation, regression scores and new predictive evidence. This focused school-level sequence requires algebra and graph reading, not calculus.
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Readiness and preparation
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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 fitting every observed point prove that a polynomial is the correct model?
Model construction and validation require different evidence.
Compare reasoning and find a refresher
No. A different polynomial can agree at all the observed inputs and disagree elsewhere. State the permitted family, domain and constraints, then evaluate predictions on observations not used to fit.
Residual signs connect numerical errors to the scatterplot.
Compare reasoning and find a refresher
Residual is observed y minus predicted y at the same x. A positive residual means the observation is above the fitted curve. Compare errors on the same response scale.