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...
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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...
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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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Sample Practice Questions

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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