Question

12. If a and B are zeroes of the polynomial f(x)
= x2 - x-k such that a - B = 9, find k.'
[CBSE 2013]
​

Answer 1

Step-by-step explanation:

we know

ab=C/a

ab=k/1

a+b =-b/a

so,

a+b = 1

squaring both sides.

a2 + b2 + 2ab = 1

putting value of ab

a2 + b2 = 1- 2k

and,

a-b = 9 (given)

squaring both the sides.

a2 +b2 -2ab = 81

putting values of a2 + b2 and ab

we get

1-2k - 2 = 81

-2k =81 +1

k=-41

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