Mathematics Grade 9 15 min

Multiply by 0

Multiply by 0

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1

Introduction & Learning Objectives

Learning Objectives Define and apply the Zero Product Property to solve polynomial equations. Identify the roots (or zeros) of a function when it is presented in factored form. Simplify complex algebraic expressions that contain a factor equivalent to zero. Differentiate between the role of zero in multiplication (annihilator) and addition (identity). Explain why an equation must be set equal to zero before the Zero Product Property can be applied. Analyze a factored expression and determine the values of a variable that make the entire expression equal to zero. If I tell you that the product of two secret numbers is zero, what can you tell me for sure about at least one of those numbers? 🤔 This tutorial explores one of the most powerful rules in algebra: multiplying by ze...
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Key Concepts & Vocabulary

TermDefinitionExample Zero Product PropertyA mathematical property stating that if the product of two or more factors is zero, then at least one of the factors must be zero.If (x - 3)(x + 5) = 0, then either (x - 3) = 0 or (x + 5) = 0. Multiplicative Property of ZeroA property stating that the product of any number and zero is zero.For any real number 'a', a * 0 = 0. For instance, (x^2 + 4x - 7) * 0 = 0. Root (or Zero) of a FunctionAn input value (x-value) that causes the output of a function f(x) to be zero. These are the x-intercepts on a graph.For the function f(x) = x - 4, the root is x = 4 because f(4) = 4 - 4 = 0. FactorA number or algebraic expression that divides another number or expression evenly—i.e., with no remainder.In the expression (x + 2)(x - 1), the factors are...
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Core Formulas

The Zero Product Property For any real numbers a and b, if a \cdot b = 0, then a = 0 or b = 0 (or both). This is the fundamental rule used to solve factored polynomial equations. If you have an equation where one side is a product of factors and the other side is zero, you can set each factor equal to zero individually and solve. The Multiplicative Property of Zero For any real number a, a \cdot 0 = 0. Use this rule to simplify expressions. If you can identify any factor in a long product that is equal to zero, the entire product simplifies to zero, regardless of the complexity of the other factors.

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Sample Practice Questions

Challenging
What is the sum of the distinct solutions to the equation (x² - 4)(x - 2) = 0?
A.0
B.2
C.4
D.-2
Challenging
A quadratic function has roots at x = 0 and x = 5. The graph of the function is a parabola that opens downwards. Which of the following could be the equation of the function?
A.f(x) = x(x + 5)
B.f(x) = -2x(x - 5)
C.f(x) = x² - 5
D.f(x) = 5x(x - 1)
Challenging
A student incorrectly applies the Zero Product Property to solve (x² - 9) = 7, reasoning that since x² - 9 = (x-3)(x+3), the solutions are x-3=7 (x=10) and x+3=7 (x=4). Which of the following values of x is an actual solution to the original equation?
A.x = 10
B.x = 3
C.x = 4
D.x = -4

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