Mathematics
Grade 11
15 min
Factor using a quadratic pattern
Factor using a quadratic pattern
Tutorial Preview
1
Introduction & Learning Objectives
Learning Objectives
Identify polynomials and other expressions that are in 'quadratic form'.
Choose an appropriate substitution to transform a complex expression into a standard quadratic trinomial.
Factor expressions of the form ax^{2n} + bx^n + c.
Factor expressions with rational or negative exponents that follow a quadratic pattern.
Use back-substitution to write the final factored form in terms of the original variable.
Recognize when a factored expression can be factored further, such as a difference of squares.
Ever feel like you're seeing the same math problem in disguise? 🤔 What if a scary-looking quartic polynomial was just a simple quadratic wearing a mask?
This tutorial will teach you how to recognize and factor expressions that follow a 'qua...
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Key Concepts & Vocabulary
TermDefinitionExample
Quadratic Form (or Pattern)An expression that can be written in the form au² + bu + c, where 'u' is itself an algebraic expression. The key feature is that the exponent of the leading term's variable part is exactly double the exponent of the middle term's variable part.The expression x⁴ + 6x² + 5 is in quadratic form because if we let u = x², it becomes u² + 6u + 5.
u-SubstitutionA technique used to simplify an expression by temporarily replacing a more complex part of it (like x² or x¹/³) with a single variable, typically 'u'.To factor x⁶ - 7x³ - 8, we substitute u = x³ to get the simpler quadratic u² - 7u - 8.
Back-SubstitutionThe final step after factoring using u-substitution, where the original expression (e.g., x²) is substituted...
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Core Formulas
The General Quadratic Form
ax^{2n} + bx^n + c
This is the standard structure to look for. If an expression fits this pattern, you can use a quadratic factoring method. The exponent of the first term (2n) must be double the exponent of the middle term (n).
The Substitution Rule
Let u = x^n
Once you identify an expression in the form ax^{2n} + bx^n + c, you make the substitution u = x^n. This transforms the expression into the standard quadratic au² + bu + c, which you can factor using familiar methods.
Difference of Squares Pattern
A^2 - B^2 = (A - B)(A + B)
This pattern is crucial because it often appears after back-substitution. Always check your factors to see if they can be factored further using this rule.
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Challenging
Factor the expression 2x⁵ + 2x³ - 12x completely.
A.2x(x² + 3)(x² - 2)
B.2x(x⁴ + x² - 6)
C.2x(x² - 3)(x² + 2)
D.x(2x⁴ + 2x² - 12)
Challenging
Factor the expression x⁴ - 5x²y² + 4y⁴ completely.
A.(x² - 4y²)(x² - y²)
B.(x - 2y)(x + 2y)(x - y)(x + y)
C.(x - 2y)(x + y)(x - y)(x + 2y)
D.(x² - 2y²)(x² - 2y²)
Challenging
Factor the expression x⁸ - 82x⁴ + 81 completely.
A.(x⁴ - 81)(x⁴ - 1)
B.(x² - 9)(x² + 9)(x² - 1)(x² + 1)
C.(x - 3)(x + 3)(x² + 9)(x - 1)(x + 1)(x² + 1)
D.(x - 3)(x + 3)(x - 1)(x + 1)
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