Correct TOMS 748 root bracketing docs

doc/html/math_toolkit/roots_noderiv/TOMS748.html

@@ -105,7 +105,7 @@
               A unary functor (or C++ lambda) that is the function whose root is
               to be solved. f(x) need not be uniformly increasing or decreasing on
               <span class="emphasis"><em>x</em></span> and may have multiple roots. However, the bounds
-              given must bracket a single root.
+              given must bracket at least one root.
             </p></dd>
 <dt><span class="term">a</span></dt>
 <dd><p>

doc/roots/roots_without_derivatives.qbk

@@ -373,7 +373,7 @@ The __root_finding_TOMS748 parameters are:
 [variablelist
 [[f]   [A unary functor (or C++ lambda) that is the function whose root is to be solved.
        f(x) need not be uniformly increasing or decreasing on ['x] and
-       may have multiple roots.  However, the bounds given must bracket a single root.]]
+       may have multiple roots.  However, the bounds given must bracket at least one root.]]
 [[a]   [The lower bound for the initial bracket of the root.]]
 [[b]   [The upper bound for the initial bracket of the root.
        It is a precondition that ['a < b] and that ['a] and ['b]