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Mathematics 2008 Question Papers

Q. 7. For what value of k, does (k 12) x2 + 2 (k 12) x + 2 = 0 have equal roots?

Sol. Here a = k 12, b = 2 (k 12), c = 2
D² = 0 …(Roots are equal)
. b 4ac = 0
. [2 (k 12)]² 4 (k 12) (2) = 0
4 (k 12)² 8 (k 12) = 0
4 (k 12) (k 12 2) = 0
(k 12) (k 14) = 0 = 0
k 12 = 0 or k 14 = 0 . k = 12 or k = 14
Rejecting k = 12, because coefficient of x2 cannot be zero
K =14

Ans. k = 14

Q. 8. What is the perimeter of a sector of angle 45° of a circle with radius 7 cm? [Use π = 22/7]

Sol.

Ans. 19.5 cm

Mathematics 2008 Question Papers Class X
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