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The polynomial $2x^3 + 6x^2 - 7x - 10$ has zeros $\alpha$, $\beta$ and $\gamma$ - HSC - SSCE Mathematics Extension 1 - Question 4 - 2018 - Paper 1

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The-polynomial-$2x^3-+-6x^2---7x---10$-has-zeros-$\alpha$,-$\beta$-and-$\gamma$-HSC-SSCE Mathematics Extension 1-Question 4-2018-Paper 1.png

The polynomial $2x^3 + 6x^2 - 7x - 10$ has zeros $\alpha$, $\beta$ and $\gamma$. What is the value of $\alpha\beta\gamma(\alpha + \beta + \gamma)$?

Worked Solution & Example Answer:The polynomial $2x^3 + 6x^2 - 7x - 10$ has zeros $\alpha$, $\beta$ and $\gamma$ - HSC - SSCE Mathematics Extension 1 - Question 4 - 2018 - Paper 1

Step 1

What is the value of $\alpha\beta\gamma(\alpha + \beta + \gamma)$?

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Answer

To find the value of αβγ(α+β+γ)\alpha\beta\gamma(\alpha + \beta + \gamma) for the polynomial given, we can use Vieta's formulas, which relate the coefficients of the polynomial to sums and products of its roots.

  1. Identify Roots: From the polynomial 2x3+6x27x102x^3 + 6x^2 - 7x - 10, Vieta's formulas tell us:

    • The product of the roots ( etaetaeta) = da=(10)2=5\frac{-d}{a} = \frac{-(-10)}{2} = 5
    • The sum of the roots (α+β+γ\alpha + \beta + \gamma) = ba=62=3\frac{-b}{a} = \frac{-6}{2} = -3.
  2. Calculate the Expression:
    Now substitute these values into the expression: αβγ(α+β+γ)=5(3)=15.\alpha\beta\gamma(\alpha + \beta + \gamma) = 5 \cdot (-3) = -15.

Thus, the required value of αβγ(α+β+γ)\alpha\beta\gamma(\alpha + \beta + \gamma) is -15.
Given the options in the question, the correct answer is B: -15.

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