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f(x)=x^(3)+5x^(2)-4x-20 How many of th...

`f(x)=x^(3)+5x^(2)-4x-20`
How many of the zeros of funtion f defined by the equation above are located in the interval `-4lexle4`?

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To find how many zeros of the function \( f(x) = x^3 + 5x^2 - 4x - 20 \) are located in the interval \([-4, 4]\), we will evaluate the function at various integer points within this interval and check for roots. ### Step-by-Step Solution: 1. **Identify the function and the interval**: \[ f(x) = x^3 + 5x^2 - 4x - 20 \] We are interested in the interval \([-4, 4]\). 2. **Determine the factors of the constant term**: The constant term of the polynomial is \(-20\). The factors of \(-20\) that we will consider within the interval are: \[ \pm 1, \pm 2, \pm 4 \] 3. **Evaluate the function at each integer in the interval**: - **For \( x = -4 \)**: \[ f(-4) = (-4)^3 + 5(-4)^2 - 4(-4) - 20 = -64 + 80 + 16 - 20 = 12 \quad (\text{not a zero}) \] - **For \( x = -3 \)**: \[ f(-3) = (-3)^3 + 5(-3)^2 - 4(-3) - 20 = -27 + 45 + 12 - 20 = 10 \quad (\text{not a zero}) \] - **For \( x = -2 \)**: \[ f(-2) = (-2)^3 + 5(-2)^2 - 4(-2) - 20 = -8 + 20 + 8 - 20 = 0 \quad (\text{zero found}) \] - **For \( x = -1 \)**: \[ f(-1) = (-1)^3 + 5(-1)^2 - 4(-1) - 20 = -1 + 5 + 4 - 20 = -12 \quad (\text{not a zero}) \] - **For \( x = 0 \)**: \[ f(0) = 0^3 + 5(0)^2 - 4(0) - 20 = -20 \quad (\text{not a zero}) \] - **For \( x = 1 \)**: \[ f(1) = 1^3 + 5(1)^2 - 4(1) - 20 = 1 + 5 - 4 - 20 = -18 \quad (\text{not a zero}) \] - **For \( x = 2 \)**: \[ f(2) = 2^3 + 5(2)^2 - 4(2) - 20 = 8 + 20 - 8 - 20 = 0 \quad (\text{zero found}) \] - **For \( x = 3 \)**: \[ f(3) = 3^3 + 5(3)^2 - 4(3) - 20 = 27 + 45 - 12 - 20 = 40 \quad (\text{not a zero}) \] - **For \( x = 4 \)**: \[ f(4) = 4^3 + 5(4)^2 - 4(4) - 20 = 64 + 80 - 16 - 20 = 108 \quad (\text{not a zero}) \] 4. **Count the zeros found**: The zeros found in the interval \([-4, 4]\) are: - \( x = -2 \) - \( x = 2 \) Thus, there are **2 zeros** of the function \( f(x) \) in the interval \([-4, 4]\). ### Final Answer: The number of zeros of the function \( f(x) \) in the interval \([-4, 4]\) is **2**.
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