Question

find the value of k for which the roots of quadratic equation (k - 4 )x2 + 2( k - 4 )x + 2 =0 are equal

Answer 1

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Answer 2

Question:

Find the value of k for which the quadratic equation (k-4)x² + 2(k-4)x + 2 = 0 has equal roots.

Answer:

k = 4 , 6

Note:

• An equation of degree 2 is know as quadratic equation .

• Roots of an equation is defined as the possible values of the unknown (variable) for which the equation is satisfied.

• The maximum number of roots of an equation will be equal to its degree.

• A quadratic equation has atmost two roots.

• The general form of a quadratic equation is given as , ax² + bx + c = 0 .

• The discriminant of the quadratic equation is given as , D = b² - 4ac .

• If D = 0 , then the quadratic equation would have real and equal roots .

• If D > 0 , then the quadratic equation would have real and distinct roots .

• If D < 0 , then the quadratic equation would have imaginary roots .

Solution:

The given quadratic equation is ;

(k-4)x² + 2(k-4)x + 2 = 0

Clearly , we have ;

a = k-4

b = 2(k-4)

c = 2

We know that ,

The quadratic equation will have equal roots if its discriminant is equal to zero .

=> D = 0

=> [2(k-4)]² - 4•(x-4)•2 = 0

=> 4(k-4)² - 4•2(k-4) = 0

=> 4(k-4)•(k-4-2) = 0

=> (k-4)(k-6) = 0

=> k = 4 , 6

Hence,

The required values of k are 4 and 6 .