At which root does the graph of f(x) = (x + 4)6(x + 7)5 cross the x-axis?

The roots are x = −4 and x = −7, from setting each factor equal to zero. At x = −4, the factor has even multiplicity 6, so the graph touches the x-axis but does not cross it. At x = −7, the factor has odd multiplicity 5, so the graph crosses the x-axis. The correct choice is −7.

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