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Khan Academy
Khan Academy: Features of Quadratic Functions
Find the zeroes ('roots') of quadratic functions and the vertex of their parabolas. Functions are given in standard, vertex, and factored form.
CK-12 Foundation
Ck 12: Algebra: Quadratic Functions and Equations
[Free Registration/Login may be required to access all resource tools.] This lesson covers vertex, intercept, and standard forms.