Question

If the sum of the zeros of the polynomial 2x3 – 3kx2 + 4x – 5 is 6, then the value
of k is
(d) 2
(c) 4
(a)-4
(b)-2​

Answer 1

Answer:

(d)2 is the answer

Explanation:

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Answer 2

Given :

Sum of the zeroes of the polynomial f(x) = 2x³– 3kx² + 4x – 5 is 6.

To find :

Value of k .

Concept :

For a cubic polynomial is in the form of ax³ + bx² + cx + d :

∵ Sum of zeros = -b/a  where, b is coefficient of x² and a is the coefficient of x³

Solution :

Now , f(x) = 2x³ - 3kx² + 4x - 5

Or, f(x) = 2x³ + (-3kx²) + 4x + (-5)

Now according to concept :

⇒ -coefficient of x²/coefficient of x³ = 6

⇒ -(-3k)/2 = 6

⇒ 3k/2 = 6

⇒ 3k = 6 × 2

⇒ 3k = 12

⇒ k = 12/3

⇒ k = 4

∴ Required value of k = 4