Mathematics
Grade 9
15 min
Find the number of solutions
Find the number of solutions
Tutorial Preview
1
Introduction & Learning Objectives
Learning Objectives
Define and identify the three possible outcomes for the number of solutions to a linear equation (one, none, infinite).
Analyze a linear equation without fully solving it to determine the number of solutions.
Calculate the discriminant of a quadratic equation in the form ax² + bx + c = 0.
Use the discriminant to determine the number of real solutions (two, one, or zero) for a quadratic equation.
Connect the number of solutions of a quadratic equation to the number of x-intercepts on the graph of its corresponding parabola.
Distinguish between finding the actual solutions and finding *how many* solutions exist.
Ever tried to solve a puzzle and wondered if there was more than one right answer, or maybe none at all? 🤔 Equations are just like that!
In this...
2
Key Concepts & Vocabulary
TermDefinitionExample
Solution (or Root)A value for a variable that makes an equation a true statement.For the equation x + 3 = 5, the solution is x = 2 because 2 + 3 = 5.
Linear EquationAn equation where the highest power of the variable is 1. Its graph is a straight line.3x - 7 = 2
Quadratic EquationAn equation where the highest power of the variable is 2, written in the standard form ax² + bx + c = 0, where a ≠ 0.x² - 4x + 3 = 0
DiscriminantThe expression b² - 4ac from the quadratic formula. Its value 'discriminates' or determines the number of real solutions a quadratic equation has.For 2x² + 5x - 3 = 0, the discriminant is 5² - 4(2)(-3) = 49.
IdentityAn equation that is true for all possible values of the variable. It has infinitely many solutions.2(x + 1) = 2x + 2 simplifi...
3
Core Formulas
Number of Solutions for Linear Equations
After simplifying a linear equation to the form ax = b:
1. One solution if a ≠ 0.
2. No solution if a = 0 and b ≠ 0.
3. Infinite solutions if a = 0 and b = 0.
Use this after simplifying a linear equation to quickly determine the number of solutions without finding the exact value. It helps classify the equation as having a unique solution, being a contradiction, or being an identity.
The Discriminant Formula
Δ = b² - 4ac
This formula is used for quadratic equations in standard form (ax² + bx + c = 0). You must identify the coefficients a, b, and c before substituting them into the formula to find the value of the discriminant (Δ).
Interpreting the Discriminant
For a quadratic equation:
1. If Δ > 0, there are two distinct...
5 more steps in this tutorial
Sign up free to access the complete tutorial with worked examples and practice.
Sign Up Free to ContinueSample Practice Questions
Challenging
For what value(s) of k does the equation x² + kx + 16 = 0 have exactly one real solution?
A.k = 4 only
B.k = 8 only
C.k = 4 or k = -4
D.k = 8 or k = -8
Challenging
For which values of k does the equation 3x² - 6x + k = 0 have no real solutions?
A.k > 3
B.k < 3
C.k = 3
D.k < -3
Challenging
Compare the number of solutions for Equation A: 4(x-1) = 4x-4 and Equation B: x² - 10x + 26 = 0.
A.has one solution; B has no solutions.
B.has no solutions; B has one solution.
C.has infinitely many solutions; B has no solutions.
D.has one solution; B has two solutions.
Want to practice and check your answers?
Sign up to access all questions with instant feedback, explanations, and progress tracking.
Start Practicing Free