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In Chapter ( [link] ) we studied linear equations in one and two variables and methods for solving them. We observed that a linear equation in one variable was any equation that could be written in the form and a linear equation in two variables was any equation that could be written in the form where and are not both 0. We now wish to study quadratic equations in one variable.
The standard form of the quadratic equation is
For a quadratic equation in standard form
is the coefficient of
is the coefficient of
is the constant term.
The following are quadratic equations.
Notice that this equation could be written
Now it is clear that
Notice that this equation could be written
Now it is clear that
The following are not quadratic equations.
The expression on the left side of the equal sign has a variable in the denominator and, therefore, is not a quadratic.
Which of the following equations are quadratic equations? Answer “yes” or “no” to each equation.
Our goal is to solve quadratic equations. The method for solving quadratic equations is based on the zero-factor property of real numbers. We were introduced to the zero-factor property in Section [link] . We state it again.
Use the zero-factor property to solve each equation.
If
then
must be 0, since 5 is not zero.
Use the zero-factor property to solve each equation.
For the following problems, write the values of and in quadratic equations.
For the following problems, use the zero-factor property to solve the equations.
( [link] ) Factor by grouping.
( [link] ) Find the difference:
( [link] ) Solve the radical equation
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