quadratic

Asked by duttaneelanjana | 11th Jul, 2009, 01:58: AM

Expert Answer:

For the QE to have equal roots  D =0.i.e  b2 -4ac = 0

here a = 1 , b = 2(1+3k) , c = 7(3 +2k)

If  b2 -4ac = 0

[2(1 +3k)]2  -4 x 1  x 7(3 +2k) = 0

4 (1+ 6k +9k2) - 4 x 1 x (21 +14k) =  0...........divide through out by 4

1+ 6k +9k2 -21 -14k = 0

9k2  - 8k - 20 = 0

9k2 -18k +10k -20 =0

9k (k -2) -10 (k -2) =0

(9k-10)(k -2) = 0

k =  -10/9 or  k = 2.

Answered by  | 11th Jul, 2009, 10:52: AM

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