Q. 3

# If one zero of the polynomial 2x^{2} + x + k is 3 then the value of k will be:

A. 12

B. 21

C. 24

D. –21

Answer :

Given one zero = 3

Let second zero a.

When we compare the above quadratic equation with the generalized one we get,

ax^{2} + bx + c = 0

∴ a = 2, b = 1, c = k

Sum of zeroes = -b/a

3 + a = -1/2

a = -1/2 – 3

a = -7/2

Product of zeroes = 3 × (-7/2)

= -21/2

Product of zeroes = c/a

k/2 = -21/2

k = -21

So the correct answer is D [-21].

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