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If `alpha` and `beta` are the roots of the equation `2x^2-3x + 4=0`, then the equation whose roots are `alpha^2` and `beta^2,` is a. `4x^(2)+7x+16=0` b. `4x^(2)+7x+6=0` c. `4x^(2)+7x+1=0` d. `4x^(2)-7x+16=0`

A

`4x^(2)+7x+16=0`

B

`4x^(2)+7x+6=0`

C

`4x^(2)+7x+1=0`

D

`4x^(2)-7x+16=0`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem step by step, we will follow the method of finding the new quadratic equation whose roots are the squares of the roots of the given equation. ### Step 1: Identify the coefficients of the given quadratic equation The given equation is: \[ 2x^2 - 3x + 4 = 0 \] Here, we have: - \( a = 2 \) - \( b = -3 \) - \( c = 4 \) ### Step 2: Calculate the sum and product of the roots Using Vieta's formulas: - The sum of the roots \( \alpha + \beta \) is given by: \[ \alpha + \beta = -\frac{b}{a} = -\frac{-3}{2} = \frac{3}{2} \] - The product of the roots \( \alpha \beta \) is given by: \[ \alpha \beta = \frac{c}{a} = \frac{4}{2} = 2 \] ### Step 3: Calculate the sum of the squares of the roots To find \( \alpha^2 + \beta^2 \), we can use the identity: \[ \alpha^2 + \beta^2 = (\alpha + \beta)^2 - 2\alpha\beta \] Substituting the values we found: \[ \alpha^2 + \beta^2 = \left(\frac{3}{2}\right)^2 - 2 \cdot 2 \] \[ = \frac{9}{4} - 4 \] \[ = \frac{9}{4} - \frac{16}{4} \] \[ = \frac{9 - 16}{4} \] \[ = \frac{-7}{4} \] ### Step 4: Calculate the product of the squares of the roots To find \( \alpha^2 \beta^2 \), we can use the identity: \[ \alpha^2 \beta^2 = (\alpha \beta)^2 \] Substituting the value of \( \alpha \beta \): \[ \alpha^2 \beta^2 = (2)^2 = 4 \] ### Step 5: Form the new quadratic equation The new quadratic equation with roots \( \alpha^2 \) and \( \beta^2 \) can be written as: \[ x^2 - (\alpha^2 + \beta^2)x + \alpha^2 \beta^2 = 0 \] Substituting the values we calculated: \[ x^2 - \left(-\frac{7}{4}\right)x + 4 = 0 \] \[ x^2 + \frac{7}{4}x + 4 = 0 \] ### Step 6: Clear the fractions To eliminate the fraction, multiply the entire equation by 4: \[ 4x^2 + 7x + 16 = 0 \] ### Final Answer Thus, the equation whose roots are \( \alpha^2 \) and \( \beta^2 \) is: \[ 4x^2 + 7x + 16 = 0 \] ### Conclusion The correct option is: **a. \( 4x^2 + 7x + 16 = 0 \)**
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