Solving equations with zero product property | Summary and Q&A

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April 3, 2017
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Khan Academy
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Solving equations with zero product property

TL;DR

By understanding that the product of two quantities equals zero only if one or both of the quantities are zero, we can solve equations and find zeros by setting each individual expression equal to zero.

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Questions & Answers

Q: Why is it necessary for one or both of the expressions to be zero in order to get the product equal to zero?

The product of two non-zero numbers will always be non-zero. Therefore, to obtain a product equal to zero, at least one of the numbers must be zero. This is a fundamental property of multiplication.

Q: What are the solutions to the equation two X minus one times X plus four equals zero?

The solutions to the equation are X equals 1/2 and X equals -4. When these values are substituted into the equation, one or both of the expressions become zero, resulting in the product equaling zero.

Q: Can an equation with multiplication have more than two solutions?

Yes, an equation with multiplication can have multiple solutions. This occurs when both expressions in the equation become zero. In the example, only one expression needs to be zero, resulting in two solutions.

Q: How can this concept be applied to functions?

To find the zeros of a function, we set the function equal to zero and solve for the variable. This sets up an equation similar to the example. By finding the values of the variable that make the function equal to zero, we determine the zeros of the function.

Summary & Key Takeaways

  • The key realization in solving the equation is that when two expressions are multiplied and equal to zero, at least one of the expressions must be equal to zero.

  • By setting each expression equal to zero - two X minus one equals zero and X plus four equals zero - we can find the solutions to the equation.

  • The equation has two solutions: X equals 1/2 or X equals -4. Substituting either value in shows that it makes one expression equal to zero, resulting in the product equaling zero.

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