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  1. For what value of k the quadratic polynomial 3z2 + 5z + k can be factored into product of real linear factors ?
    1. k ≤
      25
      6
    2. k ≤
      25
      12
    3. k ≥
      25
      12
    4. k ≥
      25
      6
Correct Option: B

We have , the given quadratic eq. 3z 2 + 5z + k
Comparing it with ax 2 + bx + c = 0, we get a = 3, b = 5, c = k
Now , D = b2 - 4ac = 25 - 12k
For equal linear factors to exist, D ≥ 0
⇒ 25 - 12k ≥ 0
⇒ 25 ≥ 12k

⇒ k ≤
25
12
Therefore, the set of real numbers ≤
25
gives the set of value of k for which the given
12
quadratic polynomial can be factored into the product of real linear factors.



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