Question

Find the value of 5x ki power 2 plus 2x minus 222 when x equal to minus 2

Answer 1

Answer:

Equation x^2+2\sqrt2 kx+18=0x

2

+2

2

kx+18=0

To find : The values of k for which the quadratic equation has equal roots ?

Solution :

The quadratic equation ax^2 + bx + c = 0ax

2

+bx+c=0 has equal roots when discriminant zero,

i.e. b^2 - 4ac = 0b

2

−4ac=0

On comparing,

a=1,\ b=2\sqrt2 k,\ c=18a=1, b=2

2

k, c=18

Substitute the values,

(2\sqrt2 k)^2-4(1)(18)= 0(2

2

k)

2

−4(1)(18)=0

8k^2-72= 08k

2

−72=0

8k^2=728k

2

=72

k^2=\frac{72}{8}k

2

=

8

72

k^2=9k

2

=9

k=\sqrt{9}k=

9

k=\pm 3k=±3

Therefore, The value of k is 3 and -3.