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

If `alpha,beta` are the roots of the equation `ax^(2)+bx+c=0` then `log(a-bx+cx^(2))` is equal to

A

`log a+(alpha+beta)x+(alpha^(2)+beta^(1))/(2)x^(2)+(alpha^(3)+beta^(3))/(3)x^(3)`+...

B

`log a +(alpha+beta) x+(alpha^(2)+beta^(2))/(2)x^(2)+(alpha^(3)+beta^(3))/(3)x^(3)`+…

C

`log a-(alpha+beta)x-(alpha^(2)+beta^(1))/(2)x^(2)-(alpha^(3)+beta^(3))/(3)x^(3)`+...

D

none of these

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The correct Answer is:
To solve the problem, we need to evaluate the expression \( \log(a - bx + cx^2) \) given that \( \alpha \) and \( \beta \) are the roots of the quadratic equation \( ax^2 + bx + c = 0 \). ### Step-by-Step Solution: 1. **Identify the Roots**: Since \( \alpha \) and \( \beta \) are the roots of the equation \( ax^2 + bx + c = 0 \), we can use Vieta's formulas: - \( \alpha + \beta = -\frac{b}{a} \) - \( \alpha \beta = \frac{c}{a} \) 2. **Rearranging the Expression**: We start with the expression \( a - bx + cx^2 \). We can rewrite it as: \[ a - bx + cx^2 = c\left(\frac{a}{c} - \frac{b}{c}x + x^2\right) \] This can also be expressed as: \[ c\left(x^2 - \frac{b}{c}x + \frac{a}{c}\right) \] 3. **Factoring the Quadratic**: The quadratic \( x^2 - \frac{b}{c}x + \frac{a}{c} \) can be factored using its roots \( \alpha \) and \( \beta \): \[ x^2 - (\alpha + \beta)x + \alpha \beta = (x - \alpha)(x - \beta) \] Substituting the values from Vieta's, we have: \[ x^2 - \left(-\frac{b}{a}\right)x + \frac{c}{a} = (x - \alpha)(x - \beta) \] 4. **Substituting Back**: Thus, we can express \( a - bx + cx^2 \) as: \[ a - bx + cx^2 = c\left(x - \alpha\right)\left(x - \beta\right) \] 5. **Taking the Logarithm**: Now, we can take the logarithm of the expression: \[ \log(a - bx + cx^2) = \log\left(c(x - \alpha)(x - \beta)\right) \] Using the properties of logarithms, we can split this into: \[ \log(c) + \log(x - \alpha) + \log(x - \beta) \] 6. **Final Expression**: Therefore, the final expression for \( \log(a - bx + cx^2) \) is: \[ \log(c) + \log(x - \alpha) + \log(x - \beta) \] ### Final Answer: \[ \log(a - bx + cx^2) = \log(c) + \log(x - \alpha) + \log(x - \beta) \]
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OBJECTIVE RD SHARMA-EXPONENTIAL AND LOGARITHMIC SERIES-Exercise
  1. The expansion of (1+(x^(2))/(2!)+(x^(4))/(4!)..)^(2) in ascending powe...

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  2. The coefficent of x^(n) in the expansion of (1+(x^(2))/(2!)+(x^(4))/(4...

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  3. If alpha,beta are the roots of the equation ax^(2)+bx+c=0 then log(a-b...

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  4. The sum of the series 1+(1+2)/(2!)+(1+2+2^(2))/(3!)+(1+2+2^(2)+2^(3)...

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  5. The sum of the series 1+(1^2+2^2)/(2!)+(1^(2)+2^(2)+3^(2))/(3!)+(1^(...

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  6. The coefficent of x^(n) in the series 1+(a+bx)/(1!)+(a+bx)^(2)/(2!)+...

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  7. The sum of the series (1^(2).2^(2))/(1!)+(2^(2).3^(2))/(2!)+(3^(2).4^(...

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  8. The value of (x+y)(x-y)+1/(2!)(x+y)(x-y)(x^2+y^2)+1/(3!)(x+y)(x-y)(x^4...

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  9. If e^(x)=y+sqrt(1+y^(2) then the value of y is

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  10. If (e^(5x)+e^(x))/(e^(3x)) is expand in a series of ascending powers o...

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  11. In the expansion of (e^(7x)+e^(3x))/(e^(5x)) the constant term is

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  12. The value of sqrt(2-1)/sqrt(2)+3-2sqrt(2)/(4)+5sqrt(2-7)/6sqrt(2)+17-1...

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  13. If y=2x^(2)-1 then (1)/(x^(2))+(1)/(2x^(4))+(1)/(3x^(6))+…infty equals...

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  14. If S=Sigma(n=2)^(oo) ""^(n)C(2) (3^(n-2))/(n!) then S equals

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  15. If (e^(x))/(1-x) = B(0) +B(1)x+B(2)x^(2)+...+B(n)x^(n)+... , then the ...

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  16. IfS=Sigma(n=1)^(oo) (""^(n)C(0)+""^(n)C(1)+""^(n)c(2)+..+""^(n)C(n))/(...

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  17. If S=Sigma(n=2)^(oo) (""^(n)C(2))/(n+1)! then S equals

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  18. 1/(1.2)+(1.3)/(1.2.3.4)+(1.3.5)/(1.2.3.4.5.6)+.....oo

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  19. The sum of the series (12)/(2!)+(28)/(3!)+(50)/(4!)+(78)/(5!)+…is

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  20. If a=sum(n=0)^(oo) (x^(3n))/((3n)!) , b=sum(n=1)^(oo) (x^(3n-2))/((3n-...

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