Question

if -4 is the root of the quadratic equation​

Answer 1

Answer:

k= -4

Step-by-step explanation:

p=3

4²+ 3*-4 + k =0

16-12+k=0

4+k=0

k=-4

Answer 2

Solution:

i) -4 is the root of the quadratic equation x²+px-4=0,

substitute x=-4 in the equation, we get

=> (-4)²+p(-4)-4=0

=> 16-4p-4 = 0

=> 12 - 4p = 0

=> -4p = -12

=> p = (-12)/(-4) = 3

p = 3 ----(1)

ii) Given x²+px+k = 0

Put p=3 in the equation , we get

x²-3x+k = 0

compare this with ax²+bx+c=0,

we get

a = 1 , b = -3 , c = k

Discreminant (D) = 0

/* Given roots are equal */

b² - 4ac = 0

=> (-3)² - 4×1×k = 0

=> 9 - 4k = 0

=> -4k = -9

=> k = (-9)/(-4)

=> k = 9/4

Therefore,

Option (D) is correct.

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