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The equation whose roots are smalle...

The equation whose roots are smaller by 1 then those of `2x ^2-5x +6=0` is

A

`2x^(2) - 9x + 13 = 0`

B

`2x^(2) - x + 3 = 0`

C

`2x^(2) + 9x + 13 = 0`

D

`2x^(2) +x + 3 = 0`

Text Solution

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The correct Answer is:
To find the equation whose roots are smaller by 1 than those of the quadratic equation \(2x^2 - 5x + 6 = 0\), we can follow these steps: ### Step 1: Identify the coefficients of the given quadratic equation The given equation is \(2x^2 - 5x + 6 = 0\). Here, we identify: - \(a = 2\) - \(b = -5\) - \(c = 6\) **Hint:** The coefficients \(a\), \(b\), and \(c\) are the numbers in front of \(x^2\), \(x\), and the constant term, respectively. ### Step 2: Calculate the sum and product of the roots Let the roots of the equation be \(\alpha\) and \(\beta\). Using Vieta's formulas: - The sum of the roots \(\alpha + \beta = -\frac{b}{a} = -\frac{-5}{2} = \frac{5}{2}\) - The product of the roots \(\alpha \beta = \frac{c}{a} = \frac{6}{2} = 3\) **Hint:** Vieta's formulas relate the coefficients of a polynomial to sums and products of its roots. ### Step 3: Determine the new roots Since we want the new roots to be smaller by 1, we have: - New roots: \(\alpha - 1\) and \(\beta - 1\) ### Step 4: Calculate the sum of the new roots The sum of the new roots is: \[ (\alpha - 1) + (\beta - 1) = \alpha + \beta - 2 = \frac{5}{2} - 2 = \frac{5}{2} - \frac{4}{2} = \frac{1}{2} \] **Hint:** To find the new sum, simply subtract 2 from the original sum of the roots. ### Step 5: Calculate the product of the new roots The product of the new roots is: \[ (\alpha - 1)(\beta - 1) = \alpha \beta - (\alpha + \beta) + 1 = 3 - \frac{5}{2} + 1 \] Calculating this gives: \[ = 3 - \frac{5}{2} + \frac{2}{2} = 3 - \frac{3}{2} = \frac{6}{2} - \frac{3}{2} = \frac{3}{2} \] **Hint:** Use the distributive property to expand the product and substitute the known values. ### Step 6: Form the new quadratic equation The new quadratic equation can be formed using the sum and product of the new roots: \[ x^2 - \text{(sum of roots)} \cdot x + \text{(product of roots)} = 0 \] Substituting the values we found: \[ x^2 - \frac{1}{2}x + \frac{3}{2} = 0 \] ### Step 7: Eliminate the fraction To eliminate the fractions, multiply the entire equation by 2: \[ 2x^2 - x + 3 = 0 \] ### Conclusion Thus, the equation whose roots are smaller by 1 than those of \(2x^2 - 5x + 6 = 0\) is: \[ \boxed{2x^2 - x + 3 = 0} \]
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