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Let f(x) = (x – 4) (x – 5) (x – 6) (x – 7) then,
  • a)
    f '(x) = 0 has four roots
  • b)
    Three roots of f'(x) = 0 lie in (4, 5) ∪ (5, 6) ∪ (6, 7)
  • c)
    The equation f'(x) = 0 has only one real root
  • d)
    Three roots of f'(x) = 0 lie in (3, 4) ∪ (4, 5) ∪ (5, 6)
Correct answer is option 'B'. Can you explain this answer?
Most Upvoted Answer
Let f(x) = (x –4) (x –5) (x –6) (x –7) then,a)...
Explanation:

Given Function:
f(x) = (x - 4)(x - 5)(x - 6)(x - 7)

Number of Roots:
a) The given function f(x) is a polynomial of degree 4, which means it can have at most 4 roots.
Therefore, f(x) = 0 has four roots.

Roots in Intervals:
b) To find the roots in the intervals (4, 5), (5, 6), and (6, 7), we need to analyze the behavior of the function in these intervals.
- In the interval (4, 5):
- f(4) = (4 - 4)(4 - 5)(4 - 6)(4 - 7) = 0
- In the interval (5, 6):
- f(5) = (5 - 4)(5 - 5)(5 - 6)(5 - 7) = 0
- In the interval (6, 7):
- f(6) = (6 - 4)(6 - 5)(6 - 6)(6 - 7) = 0
Therefore, three roots of f(x) = 0 lie in the intervals (4, 5), (5, 6), and (6, 7).

Real Roots:
c) The given function is a polynomial of degree 4, so it can have up to 4 real roots.
Therefore, the equation f(x) = 0 can have more than one real root.

Roots in Other Intervals:
d) The intervals (3, 4), (4, 5), and (5, 6) also contain roots of the function f(x) = 0, as the function changes sign in these intervals. However, the question specifically asks about the intervals (4, 5), (5, 6), and (6, 7).
Therefore, the correct answer is option 'b', as three roots of f(x) = 0 lie in the intervals (4, 5), (5, 6), and (6, 7).
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Let f(x) = (x –4) (x –5) (x –6) (x –7) then,a)f (x) = 0 has four rootsb)Three roots of f(x) = 0 lie in (4, 5) ∪ (5, 6) ∪ (6, 7)c)The equation f(x) = 0 has only one real rootd)Three roots of f(x) = 0 lie in (3, 4) ∪ (4, 5) ∪ (5, 6)Correct answer is option 'B'. Can you explain this answer?
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