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The polynomial P(x)=x^(3)+ax^(2)+bx+c ha...

The polynomial `P(x)=x^(3)+ax^(2)+bx+c` has the property that the mean of its roots, the product of its roots, and the sum of its coefficients are all equal. If the `y`-intercept of the graph of `y=P(x)` is `2`,
The value of `P(1)` is

A

`0`

B

`-1`

C

`2`

D

`-2`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to analyze the polynomial \( P(x) = x^3 + ax^2 + bx + c \) using the given conditions. ### Step 1: Understand the properties of the polynomial 1. The mean of the roots of the polynomial is given by: \[ \text{Mean} = \frac{\alpha + \beta + \gamma}{3} \] where \( \alpha, \beta, \gamma \) are the roots of the polynomial. 2. From Vieta's formulas, we know: - The sum of the roots \( \alpha + \beta + \gamma = -a \) - The product of the roots \( \alpha \beta \gamma = -c \) ### Step 2: Set up the equations based on the given conditions From the problem, we have three quantities that are equal: - Mean of the roots - Product of the roots - Sum of the coefficients Thus, we can write: \[ \frac{-a}{3} = -c = 1 + a + b + c \] ### Step 3: Use the y-intercept information The y-intercept of the polynomial \( P(x) \) is given as \( P(0) = c \). Since it is stated that the y-intercept is 2, we have: \[ c = 2 \] ### Step 4: Substitute \( c \) into the equations Now substituting \( c = 2 \) into our previous equations: 1. From the product of the roots: \[ -c = -2 \implies c = 2 \] 2. From the mean of the roots: \[ \frac{-a}{3} = -2 \implies -a = -6 \implies a = 6 \] 3. Substitute \( a \) and \( c \) into the sum of coefficients: \[ 1 + a + b + c = 1 + 6 + b + 2 = 9 + b \] Setting this equal to \(-2\) (from the product of the roots): \[ 9 + b = -2 \implies b = -2 - 9 = -11 \] ### Step 5: Calculate \( P(1) \) Now we have \( a = 6 \), \( b = -11 \), and \( c = 2 \). We can calculate \( P(1) \): \[ P(1) = 1^3 + 6 \cdot 1^2 - 11 \cdot 1 + 2 \] \[ P(1) = 1 + 6 - 11 + 2 = -2 \] ### Final Answer Thus, the value of \( P(1) \) is: \[ \boxed{-2} \]

To solve the problem, we need to analyze the polynomial \( P(x) = x^3 + ax^2 + bx + c \) using the given conditions. ### Step 1: Understand the properties of the polynomial 1. The mean of the roots of the polynomial is given by: \[ \text{Mean} = \frac{\alpha + \beta + \gamma}{3} \] where \( \alpha, \beta, \gamma \) are the roots of the polynomial. ...
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