How can I find the x-intercept of a cubic polynomial?

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To find the x-intercept of the cubic polynomial f(x) = x^3 + 3x^2 - 9x + 5, evaluate the function at the integer factors of the constant term, which are ±1 and ±5. Calculate f(1), f(-1), f(5), and f(-5) to identify which value yields zero. If f(1) equals zero, then x = 1 is an x-intercept, indicating that (x - 1) is a factor of the polynomial. Perform polynomial long division using (x - 1) to simplify the function and find additional x-intercepts. This method allows for a systematic approach to determining the x-intercepts of the cubic polynomial.
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I have to sketch the graph of this function:
f(x) = x^3 + 3x^2 - 9x +5

But how can I find the x-intercept (where y = 0) in this function?
 
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for cubic polynomials in order to find the x intercepts you need to look at hte integer factors of the constant (x^0) term
here look at the factors of 5 they are
+/-1,+/-5
so find f(1), f(-1), f(5), f(-5) and determine which one is zero
SUPPOSE (not necessarily true) f(1) = 0, then x = 1, and x-1 is a factor

thereafter long divide the polynomial by x-1 and then you can find more intercepts easily from the factored form.
 
Question: A clock's minute hand has length 4 and its hour hand has length 3. What is the distance between the tips at the moment when it is increasing most rapidly?(Putnam Exam Question) Answer: Making assumption that both the hands moves at constant angular velocities, the answer is ## \sqrt{7} .## But don't you think this assumption is somewhat doubtful and wrong?

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