Home
Class 12
MATHS
Assertion (A) : If alpha, beta are the r...

Assertion (A) : If `alpha, beta` are the roots of `ax^(2) + bx + c = 0` then the equation whose roots are `(alpha-1)/(alpha), (beta-1)/(beta)` is `c(1-x)^(2)+ b(1-x)+a=0`
Reason (R): If `alpha, beta` are the roots of f(x) = 0 then the equation whose roots are `(alpha-1)/(alpha)` and `(beta-1)/(beta)` is `f((1)/(1-x))=0`

A

Both A, R are true and R explain Assertion

B

Both A, R are true but R does't explain A

C

A is true R is false

D

A is false R is true

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to verify the assertion and reason provided in the question. We will derive the quadratic equation whose roots are \((\alpha - 1)/\alpha\) and \((\beta - 1)/\beta\) given that \(\alpha\) and \(\beta\) are the roots of the equation \(ax^2 + bx + c = 0\). ### Step 1: Identify the roots and their relationships The roots of the quadratic equation \(ax^2 + bx + c = 0\) are \(\alpha\) and \(\beta\). By Vieta's formulas, we know: - Sum of roots: \(\alpha + \beta = -\frac{b}{a}\) - Product of roots: \(\alpha \beta = \frac{c}{a}\) ### Step 2: Find the new roots We need to find the new roots: \[ r_1 = \frac{\alpha - 1}{\alpha}, \quad r_2 = \frac{\beta - 1}{\beta} \] ### Step 3: Calculate the sum of the new roots The sum of the new roots \(r_1 + r_2\) is: \[ r_1 + r_2 = \frac{\alpha - 1}{\alpha} + \frac{\beta - 1}{\beta} \] To combine these fractions, we find a common denominator: \[ = \frac{(\alpha - 1)\beta + (\beta - 1)\alpha}{\alpha\beta} \] Expanding the numerator: \[ = \frac{\alpha\beta - \beta + \alpha\beta - \alpha}{\alpha\beta} = \frac{2\alpha\beta - (\alpha + \beta)}{\alpha\beta} \] Substituting the values from Vieta's formulas: \[ = \frac{2\left(\frac{c}{a}\right) + \frac{b}{a}}{\frac{c}{a}} = \frac{2c + b}{c} \] ### Step 4: Calculate the product of the new roots The product of the new roots \(r_1 \cdot r_2\) is: \[ r_1 \cdot r_2 = \frac{\alpha - 1}{\alpha} \cdot \frac{\beta - 1}{\beta} = \frac{(\alpha - 1)(\beta - 1)}{\alpha\beta} \] Expanding the numerator: \[ = \frac{\alpha\beta - \alpha - \beta + 1}{\alpha\beta} = \frac{\frac{c}{a} - \left(-\frac{b}{a}\right) + 1}{\frac{c}{a}} = \frac{c + b + a}{c} \] ### Step 5: Form the quadratic equation Now that we have the sum and product of the new roots: - Sum of roots: \(S = \frac{2c + b}{c}\) - Product of roots: \(P = \frac{a + b + c}{c}\) The quadratic equation can be expressed as: \[ x^2 - Sx + P = 0 \] Substituting \(S\) and \(P\): \[ x^2 - \frac{2c + b}{c}x + \frac{a + b + c}{c} = 0 \] Multiplying through by \(c\) to eliminate the fraction: \[ cx^2 - (2c + b)x + (a + b + c) = 0 \] ### Step 6: Rearranging the equation Rearranging the equation gives: \[ c x^2 - (2c + b)x + (a + b + c) = 0 \] ### Step 7: Final form of the quadratic equation This can be rearranged to match the form given in the assertion: \[ c(1 - x)^2 + b(1 - x) + a = 0 \] Thus, the assertion is true. ### Conclusion Both the assertion and the reason provided are true, but the reason does not explain the assertion directly. Therefore, the answer is that both A and R are true, but R does not explain A.
Promotional Banner

Similar Questions

Explore conceptually related problems

If alpha, beta are the roots of x^(2)+2x+5=0 , then the equation whose roots are (alpha+1)/(alpha), (beta+1)/(beta) is

If alpha, beta are the roots of x^(2) + x + 1 = 0 , then the equation whose roots are (1)/(alpha^(3)), (1)/(beta^(3)) is

If alpha, beta are the roots of x^(2)+6x+9=0 , then the equation whose roots are (1)/(alpha), (1)/(beta) is

If alpha, beta are the roots of ax^2 + bx + c = 0, the equation whose roots are 2 + alpha, 2 + beta is

If alpha, beta are the roots of ax^(2) + bx + c = 0 then the equation with roots (1)/(aalpha+b), (1)/(abeta+b) is

If alpha, beta are the roots of x^(2)+2x-1=0 , then the equation whose roots are alpha^(2), beta^(2) is

If alpha, beta are the roots of x^(2)+x+1=0 , then the equation whose roots are alpha^(5), beta^(5) is

If alpha, beta are the roots of x^(2)-3x+1=0 , then the equation whose roots are (1/(alpha-2),1/(beta-2)) is

If alpha and beta are the roots of ax^(2)+bx+c=0 , form the equation whose roots are (1)/(alpha) and (1)/(beta) .

If alpha, beta are the roots of x^(2)+3x+1=0 , then the equation whose roots 2-alpha, 2-beta is