Basic functions: Polynomial functions
Root equations
A root equation is an equation in which a root form is present. A common scheme for solving such an equation is as follows:
- Isolate the root form.
- Take the squares of the left- and right-hand sides and solve the resulting equation.
- Check whether the solutions of the squared equation are valid solutions of the original equation
Example
\[x=\sqrt{x+3}-1\]
- isolate the root: \(\sqrt{x+3}=x+1\)
- Square and solve:
\(x+3=(x+1)^2=x^2+2x+1\) gives \(x^2+x-2=0\) or \((x+2)(x-1)=0\) and so
\(x=-2\) or \(x=1\). - Substitution of \(x=-2\) into \(\sqrt{x+3}=x+1\) gives \(1=-1\) and therefore \(x=-2\) is not a valid solution.
The solution \(x=1\) is valid.
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