Question

The value of k for which equation 9x² + 8kx has two equal roots is
(a) only 3
(b) only -3
(c) ± 3
(d) 9​

Answer 1

Answer:

c)+-3

Step-by-step explanation:

For the equation to have equal roots ,

The value of determinant should be zero.

i.e. D=b²-4ac=0———(1)

Where in this case,

b=8k

a=9 , and

c=16

Substituting the above values in (1)

=>64k²-4*9*16=0

=>64k²-576=0

=>64k²=576

=>k²=576/64

=>k²=9

=>k=+3 or -3

Hence , for the equation nto have equal roots the value of k is either +3 or -3

so ans. is c)+-3

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