Question

If one zero of quadratic polynomial 3x2 + kx _2 is -2. Then find value of k​

Answer 1

GIVEN :

Quadratic polynomial = 3x² + kx - 2

One of the zeroes = -2

P(-2) = 3x² + kx - 2

0 = 3(-2)² + k(-2) - 2

=> 0 = 3(2) - 2k - 2

=> 0 = 6 - 2k - 2

=> 0 = 4 - 2k

=> 2k = 4

=> k = 4/2

=> k = 2

VERIFICATION :

3x² + kx - 2 = 0

3(-2)² + 2(-2) - 2 = 0

=> 3(2) - 4 - 2 = 0

=> 6 - 6 = 0

=> 0 = 0

Therefore, the value of k is 2.

Answer 2

QUESTIONS—

Equations f(x)= 3x²+ kx - 2 having zeros -2. Value of k?

$\bf\huge\boxed{Answers}$

Concept-

Quadratic equation having zeroes, equation must satisfy the given zeroes.

Solution -

f(x)= 3x²+ kx - 2

putting x= -2

f(-2) = 3 (-2)² + k(-2) - (-2) = 0

=>3×4 - 2k + 2 =0

=>14 - 2k = 0

=>2k = 14

=>k = 7

Verification-

Equations must satisfy k=7 & x= - 2

= 3 (-2)² + 7(-2) - (-2)

=12 - 14 + 2

= 0

Hence verified

Conclusion-

k=7 satisfy the equation which gives a zero as - 2

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