Problem: The values of k for which the equation 2x2−kx+x+8=0 will have real and equal roots are:
Answer Choices:
A. 9 and −7
B. only −7
C. 9 and 7
D. −9 and −7
E. only 9
Solution:
2x2−x(k−1)+8=0. For real, equal roots, the discriminant (k−1)2−64=0 and k−1=±8.∴k=9 or −7.