Q. 2

# Find the value of

Given: quadratic equation kx2 - 14x + 8 = 0, one of its root is 2

To find: the value of ‘k’

Explanation: Given 2 is the root of the given equation hence the 2 must satisfy the given equation.

So now putting x = 2 in the given equation, we get

kx2 - 14x + 8 = 0

k(2)2 - 14(2) + 8 = 0

4k - 28 + 8 = 0

4k - 20 = 0

4k = 20

k = 5

Hence the value of k is 5.

OR

Given: quadratic equation x2 + 5kx + 16 = 0, it has real and equal roots

To find: the value of ‘k’

Explanation: The given quadratic equation has real and equal roots, so its determinant will be equal, i.e.,

D = 0

But we know determinant is b2 - 4ac

Hence for real and equal roots, we get

b2 - 4ac = 0………..(i)

Now comparing the given quadratic equation x2 + 5kx + 16 = 0

With the standard quadratic equation ax2 - bx + c = 0, we get

a = 1, b = 5k, c = 16

Substituting these values in equation (i), we get

b2 - 4ac = 0

(5k)2 - 4(1)(16) = 0

25k2 - 64 = 0

25k2 = 64 Taking square root on both sides, we get  Hence the value of k is Rate this question :

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