Mathematics
Grade 12
15 min
Solve a quadratic equation using square roots
Solve a quadratic equation using square roots
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1
Introduction & Learning Objectives
Learning Objectives
Identify quadratic equations in a form suitable for the square root method.
Isolate a squared variable term or a squared binomial term.
Apply the square root property to solve for a variable, including the use of '±'.
Simplify solutions involving radicals.
Determine real and complex solutions for quadratic equations.
Connect the solutions of the equation f(x) = 0 to the x-intercepts of the graph of the quadratic function y = f(x).
How can we find the exact moment a diver hits the water or the initial dimensions of a square field given its final area? 🎯 This method gives us a direct path to the answer!
This tutorial focuses on a powerful and efficient algebraic technique: solving quadratic equations using the square root property. This method i...
2
Key Concepts & Vocabulary
TermDefinitionExample
Quadratic EquationAn equation that can be written in the standard form ax² + bx + c = 0, where a, b, and c are constants and a ≠ 0.3x² - 12 = 0 is a quadratic equation where b = 0, making it ideal for the square root method.
Square Root PropertyA principle stating that if a squared expression equals a constant, the expression itself is equal to the positive and negative square root of that constant.If x² = 25, then the Square Root Property tells us that x = ±√25, so x = 5 or x = -5.
Isolating the Squared TermThe process of using inverse operations (SADMEP) to get the term containing the exponent of 2 by itself on one side of the equation.To isolate x² in 2x² - 18 = 0, you first add 18 to both sides (2x² = 18), then divide by 2 (x² = 9).
RadicandThe number or expressi...
3
Core Formulas
The Square Root Property
If x² = k, then x = ±√k
This is the fundamental rule for this method. When you take the square root of both sides of an equation to undo a square, you must account for both the positive and negative roots. This applies if k is positive, negative, or zero.
General Form for Square Root Method
To solve a(x - h)² = k, the solution is x = h ± √(k/a)
This formula is a direct application for quadratic equations in vertex form, y = a(x-h)² + k, when finding the x-intercepts (y=0). First, isolate the squared binomial, then apply the square root property, and finally solve for x.
Rule for Negative Radicands
For any positive real number k, √(-k) = i√k
When isolating the squared term results in it being equal to a negative number, the solutions will be c...
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Challenging
A quadratic equation is solved using the square root method, and its solutions are x = -4 ± 2i. Which of the following could have been the equation in the step just before the final answer was found?
A.(x + 4)² = 4
B.(x - 4)² = -2
C.(x + 4)² = -2
D.(x + 4)² = -4
Challenging
Given the equation (x - c)² = 9k⁴ where c is a real number and k is a positive real number, solve for x in terms of c and k.
A.x = c ± 3k
B.x = c ± 3k²
C.x = -c ± 3k²
D.x = c ± 9k²
Challenging
Without completely solving, what is the sum of the two solutions for the equation 2(x - 7)² + 50 = 0?
A.10i
B.7
C.14
D.-14
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