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If alpha, beta are roots of the equatio...

If `alpha, beta` are roots of the equation `ax^2 + bx + c = 0` then the equation whose roots are `2alpha + 3beta` and `3alpha + 2beta` is

A

`ab x^(2) - (a+b) cx + (a+b)^(2) = 0`

B

`ac x^(2) -(a+c) bx + (a + c)^(2) = 0`

C

`ac x^(2) + (a+c) bx -(a+c) bx -(a+c)^(2) = 0`

D

none of these

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The correct Answer is:
To find the equation whose roots are \(2\alpha + 3\beta\) and \(3\alpha + 2\beta\), we start with the given quadratic equation: \[ ax^2 + bx + c = 0 \] where \(\alpha\) and \(\beta\) are the roots. From Vieta's formulas, we know: 1. The sum of the roots \(\alpha + \beta = -\frac{b}{a}\) 2. The product of the roots \(\alpha \beta = \frac{c}{a}\) ### Step 1: Calculate the new roots Let: \[ A = 2\alpha + 3\beta \] \[ B = 3\alpha + 2\beta \] ### Step 2: Find the sum of the new roots The sum of the new roots \(A + B\) is: \[ A + B = (2\alpha + 3\beta) + (3\alpha + 2\beta) = 5\alpha + 5\beta = 5(\alpha + \beta) \] Substituting the value of \(\alpha + \beta\): \[ A + B = 5\left(-\frac{b}{a}\right) = -\frac{5b}{a} \] ### Step 3: Find the product of the new roots The product of the new roots \(A \cdot B\) is: \[ A \cdot B = (2\alpha + 3\beta)(3\alpha + 2\beta) \] Expanding this: \[ A \cdot B = 6\alpha^2 + 4\alpha\beta + 9\alpha\beta + 6\beta^2 = 6\alpha^2 + 13\alpha\beta + 6\beta^2 \] Now, we can express \(\alpha^2 + \beta^2\) in terms of \(\alpha + \beta\) and \(\alpha \beta\): \[ \alpha^2 + \beta^2 = (\alpha + \beta)^2 - 2\alpha\beta = \left(-\frac{b}{a}\right)^2 - 2\left(\frac{c}{a}\right) = \frac{b^2}{a^2} - \frac{2c}{a} \] Thus: \[ A \cdot B = 6\left(\frac{b^2}{a^2} - \frac{2c}{a}\right) + 13\left(\frac{c}{a}\right) \] \[ = \frac{6b^2}{a^2} - \frac{12c}{a} + \frac{13c}{a} = \frac{6b^2}{a^2} + \frac{c}{a} \] ### Step 4: Form the new quadratic equation The new quadratic equation with roots \(A\) and \(B\) can be expressed as: \[ x^2 - (A + B)x + (A \cdot B) = 0 \] Substituting the values we found: \[ x^2 - \left(-\frac{5b}{a}\right)x + \left(\frac{6b^2}{a^2} + \frac{c}{a}\right) = 0 \] Multiplying through by \(a^2\) to eliminate the denominators: \[ a^2x^2 + 5abx + (6b^2 + ac) = 0 \] ### Final Result Thus, the required equation whose roots are \(2\alpha + 3\beta\) and \(3\alpha + 2\beta\) is: \[ a^2x^2 + 5abx + (6b^2 + ac) = 0 \] ---
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OBJECTIVE RD SHARMA ENGLISH-QUADRATIC EXPRESSIONS AND EQUATIONS -Exercise
  1. If one root of x^(2) + px+12 = 0 is 4, while the equation x ^(2)...

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  2. if the difference of the roots of the equation x^(2)-px +q=0 is unity...

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  3. If alpha, beta are roots of the equation ax^2 + bx + c = 0 then the...

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  4. The number of roots of the equation, x-2/(x-1)=1-2/(x-1) is 0 (b) 1 ...

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  5. The number of real roots of the equation x^(2)-3|x|+2=0 is

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  6. If the equation a/(x-a)+b/(x-b)=1has two roots equal in magnitude and ...

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  7. If one of the roots of the equation ax^2 + bx + c = 0 be reciprocal ...

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  8. If sin alpha and cos alpha are roots of the equation px^2 + qx+r=0 th...

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  9. If x-c is a factor of order m of the polynomial f(x) of degree n (1 < ...

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  10. If x-c is a factor of order m of the polynomial f(x) of degree n (1 < ...

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  11. If a and b are two distinct real roots of the polynomial f(x) such th...

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  12. If ax^3+ bx - c is divisible by x^2+bx+c, then 'a' is a root of the ...

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  13. If alpha,beta are the roots of x^2+p x+q=0a n dx^(2n)+p^n x^n+q^n=0a n...

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  14. Root (s) of the equation 9x ^(2) -18|x|+5=0 belonging to the domain of...

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  15. If x=1+i is a root of the equation =x^3-i x+1-i=0, then the other real...

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  16. Let a, b, c be real numbers, a != 0. If alpha is a zero of a^2 x^2+bx...

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  17. If alphaa n dbeta are the roots of x^2+p x+q=0a n dalpha^4,beta^4 are ...

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  18. The equation (cosp-1)^x^2+(cos p)x+s in p=0 in the variable x has real...

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  19. The number of real solution of the equation. sin(e^(x))=5^(x)+5^(-x) ...

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  20. Suppose that f(x) is a quadratic expresson positive for all real xdot ...

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