Question

1. If one zero of the quadratic polynomial x2 + 3k + k is 2, then the value of k is
(a) 10
(b)-10
(c) 5
(d) -5.​

Answer 1

$\bold{Correct\: Question:}$

If one zero of the quadratic polynomial x2 + 3x + k is 2, then the value of k is

a) 10

b) - 10

c) 5

d) -5

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Solution:

x² + 3x + k = 0

and one zero is 2 means x = 2

_____________ [GIVEN]

$\implies$ x² + 3x + k = 0

$\implies$ (2)² + 3(2) + k = 0

$\implies$ 4 + 6 + k = 0

$\implies$ k = - 10

______________________________

$\textbf{k = - 10}$

Option b)

______________ [ANSWER]

______________________________

Answer 2

given one zero of the polynomial p(x) = x² + 3k + k is 2

putting value of x = 2 in p(x)

p(2) = (2)² + 3k + k

= 4 + 4k ---------(i)

equating (i) with 0

➡ 4 + 4k = 0

➡ 4k = -4

➡ k = -4/4

➡ k = -1

VERIFICATION :-

= 4 + 4(-1)

= 4 - 4

= 0

hence, the value of k is -1

but it's not given in the options.

so I guess the question might be = x² + 3x + k

p(2) = (2)² + 3(2) + k

= 4 + 6 + k

= 10 + k

equating with 0

➡ 10 + k = 0

➡ k = -10

hence, the correct option is b) -10