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Let f(x)=a x^2+bx +c a ,b ,c in R. If...

Let `f(x)=a x^2+bx +c `a ,b ,c` in R`. If `f(x)` takes real values for real values of `x` and non-real values for non-real values of `x` , then (a)`a=0` (b) `b=0` (c) `c=0` (d) nothing can be said about `a ,b ,c`.

A

Statement-1 is True, Statement-2 is True, Statement-2 is a correct explanation for Statement-1.

B

Statement-1 is True, Statement-2 is True, Statement-2 is not a correct explanation for Statement-1.

C

Statement-1 is True, Statement-2 is False.

D

Statement-1 is False, Statement-2 is True.

Text Solution

Verified by Experts

The correct Answer is:
C

If `a ne 0`, then `f(x) = {(x+(b)/(2a))^(2)+(4ac-b^(2))/(4a^(2))}`
Clearly, `f((-b)/(2a)+i)=a(-1+(4ac-b^(2))/(4a^(2)))`, which is real.
This contradicts that f(x) assumes only non-real values for non-real values of x. Therefore, a = 0.
So, Statement-1 is true.
Statement-2 is false, because - i is a root of `x^(2) + x + 1 + i = 0` but i is not its root.
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  7. Statement-1: If x^(2) + ax + 4 gt 0 "for all" x in R, then a in (-4, 4...

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  8. If the roots of the equation ax^2 + bx + c = 0, a != 0 (a, b, c are re...

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  9. Statement (1) : If a and b are integers and roots of x^2 + ax + b = 0 ...

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  11. Let f(x)=a x^2+bx +c a ,b ,c in R. If f(x) takes real values for re...

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  12. Statement-1: If a, b, c in R and 2a + 3b + 6c = 0, then the equation a...

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  13. Statement-1: If a ne 0 and the equation ax^(2) + bx + c = 0 has two ro...

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  14. Statement-1: If a, b, c in Q and 2^(1//3) is a root of ax^(2) + bx + c...

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  15. Statement-1: If f(x) = 1 + x + (x^(2))/(2!) + (x^(3))/(3!) + (x^(4))/(...

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  16. Given that for all real x, the expression (x^(2)-2x+4)/(x^(2)+2x+4) l...

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  17. Let a, b, c be real numbers such that ax^(2) + bx + c = 0 and x^(2) + ...

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  18. Statement-1: The cubic equation 4x^(3) - 15x^(2)+14x-5 = 0 has a root ...

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  19. Statement-1: The equation (pi^(e))/(x-e)+(e^(pi))/(x-pi)+(pi^(pi)+e^(e...

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  20. Consider a quadratic equation ax^(2) + bx + c = 0, where 2a + 3b + 6c ...

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