1.

Let `f(x)=x^2+b x+c ,w h e r eb ,c in Rdot`If `f(x)`is a factor of both `x^4+6x^2+25a n d3x^4+4x^4+28 x+5`, then the least value of `f(x)`is`2`b. `3`c. `5//2`d. `4`A. 2B. 3C. `5//2`D. 4

Answer» Correct Answer - 4
`f(x) = x^(2) + bx + c`
f(x) is factor of both `x^(4) + 6x^(2) + 25 and 3x^(4) + 4x^(2) + 28x + 5`
`therefore` f(x) will also be factor of
`3(x^(4) + 6x^(2) + 25) - (3x^(4) + 4x^(2) + 28x + 5) = 14(x^(2) - 2x + 5)`
`therefore x^(2) - 2x + 5` and f(x) have both roots common hence least value of
`f(x) = (x - 1)^(2) + 4 ge 4`


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