Which statement describes the graph of f(x) = 4x7 + 40x6 + 100x5?
The graph crosses the x axis at x = 0 and touches the x axis at x = 5.
The graph touches the x axis at x = 0 and crosses the x axis at x = 5.
The graph crosses the x axis at x = 0 and touches the x axis at x = -5.
The graph touches the x axis at x = 0 and crosses the x axis at x = -5.
Solution:
Given f(x) = 4x7 + 40x6 + 100x5
It can be written as
f(x) = 4x5 (x2 + 10x + 25)
Here
4x5 = 0 or x2 + 10x + 25 = 0
By further simplification
x = 0 or (x + 5)2 = 0
So we get
x = 0 or x = -5
Therefore, the graph crosses the x axis at x = 0 and touches the x axis at x = -5.
Which statement describes the graph of f(x) = 4x7 + 40x6 + 100x5?
Summary:
The statement “the graph crosses the x axis at x = 0 and touches the x axis at x = -5” describes the graph of f(x) = 4x7 + 40x6 + 100x5.
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