Question

The value of k for which the equation 2x2 – (k-1) x+8=0 will have real and equal roots are :
(a) 9 and -7
(b) only 9
(C) only - 7
(d) -9 and - 7

Answer 1

Answer:

option a is correct, i.e. 9 and -7

Step-by-step explanation:

since roots are equal and real.

so, D=0

D=b²-4ac

so, b²-4ac=0

(-(k-1))²-4×2×8=0

k²-2k+1-64=0

k²-2k-63=0

k²-9k+7k-63=0

k(k-9)+7(k-9)=0

(k-9)(k+7)=0

so, k=9, -7