Q. 7 B5.0( 1 Vote )

# Find the value of k, so that the quadratic equation(k + 1) x2 – 2 (k — 1) x + 1 = 0 has equal roots.

Since roots are equal

d=0 ….(1)

(k + 1)x2 — 2 (k – 1) x + 1 = 0

d = b2 – 4ac

d = (–2(k–1))2– 4(k+1)(1)

d = (–2k+2)2 – 4k – 4

d=4k2 + 4 – 8k – 4k – 4

( (a + b)2 = a2 + b2 + 2ab)

d = 4k2 – 12k

From (1), d = 0

Equation will be:

0 = 4k2 – 12k

4k2 = 12k k2 = 3k

k2 – 3k = 0

k(k – 3) = 0

k = 0 or k – 3 = 0

k = 3

Values of k are 0, 3.

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