Question

Find the value of K if 5 is the Zero of a quadratic polynomial x2 - Kx - 15
a) 2
b) 4
c) 6
d) 3​

Answer 1

Answer:

(a) is the correct option

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Answer 2

${ \large{ \sf{ \underline{ \color{purple}{Given : }}}}}$

$\sf{5 \: is \: the \: Zero \: of \: quadratic \: polynomial \: { \underline{ {x}^{2} - k(x) - 15}}}$

${ \large{ \sf{ \underline{ \color{purple}{ Solution: }}}}}$

$\sf{put \: (x = 5) \: in \: the \: quadratic \: equation \: {x}^{2} - k(x) - 15 \: and \: equate \: it \: to \: 0}$

$\leadsto\sf \red{ {5}^{2} - k(5) - 15 = 0} \: \:\tiny - - - -\: \:equation\:(1)$

• Solve the equation (1) and find the value of ( K ).

${ \sf{ : \implies \: {(5)}^{2} - k(5) - 15 = 0}}$

${ \sf{ : \implies \:(25) - 5(k) - 15 = 0}}$

${ \sf{ : \implies \: (10) - 5(k) = 0}}$

${ \sf{ : \implies \: 5(k) = 10}}$

${ \sf{ : \implies \: k = \frac{10}{5} }}$

${ \sf{ : \implies \: \:k = \cancel{ \frac{10}{5}} = 2 }}$

$\circ \: \: \: { \underline{ \boxed{ \pink{ \sf{ : \implies \: \:k = 2}}}}}$

• since the value of k is 2 .

$\sf{Thus, \: option \: (a) \: is \: the \: correct \: answer}$