Mathematics
Grade 12
15 min
Solve equations using a quadratic pattern
Solve equations using a quadratic pattern
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1
Introduction & Learning Objectives
Learning Objectives
Identify equations that are 'quadratic in form' even if they are not degree 2.
Apply the technique of u-substitution to transform a complex equation into a standard quadratic equation.
Solve the transformed quadratic equation for the intermediate variable 'u' using factoring, completing the square, or the quadratic formula.
Perform back-substitution to solve for the original variable in the equation.
Find all possible real and complex solutions for the original equation.
Verify solutions and identify any extraneous roots, particularly in equations with rational exponents or radicals.
Ever see a monstrous equation like x⁶ + 7x³ - 8 = 0 and feel overwhelmed? What if I told you it's just a simple quadratic equation in disguise? 🥸
T...
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Key Concepts & Vocabulary
TermDefinitionExample
Quadratic in FormAn equation that can be written in the form au² + bu + c = 0, where 'u' is an algebraic expression involving another variable. 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 equation x⁴ - 13x² + 36 = 0 is quadratic in form because it can be written as (x²)² - 13(x²) + 36 = 0.
U-SubstitutionA method used to simplify equations that are quadratic in form. We define a new variable, typically 'u', to represent the variable part of the middle term.For x⁴ - 13x² + 36 = 0, we let u = x². The equation then becomes u² - 13u + 36 = 0.
Back-SubstitutionThe final step after solving for 'u'. We replace 'u' with its origi...
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Core Formulas
The Quadratic Form Pattern
ax^{2n} + bx^n + c = 0
This is the general structure of an equation that is quadratic in form. To solve it, let u = xⁿ. This substitution transforms the equation into the standard quadratic form au² + bu + c = 0.
The Quadratic Formula
u = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}
A reliable tool for solving the transformed equation au² + bu + c = 0 when it cannot be easily factored. Remember that 'a', 'b', and 'c' are the coefficients from the transformed equation.
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Easy
For the equation (x² + 1)² - 7(x² + 1) + 10 = 0, what is the most appropriate choice for u-substitution to transform it into a standard quadratic equation?
A.u = x²
B.u = x² + 1
C.u = (x² + 1)²
D.u = x
Easy
Which of the following equations is considered 'quadratic in form'?
A.x³ - 2x² + 1 = 0
B.x⁴ - 3x + 2 = 0
C.x⁶ + 5x³ - 14 = 0
D.x⁵ - x² + 6 = 0
Easy
A student solves the equation x⁴ - 13x² + 36 = 0 using u-substitution with u = x². They correctly find that u = 4 or u = 9. What is the next critical step they must perform?
A.The solutions are 4 and 9.
B.Check for extraneous roots.
C.Perform back-substitution to solve for x.
D.Use the quadratic formula.
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