Question

Find the value of k for which the polynomial 21a^-3k+7 has real roots​

Answer 1

Answer:

for 21a^2-3k+7 to have real roots

D≥0

D=b^2-4ac

b^2-4ac ≥0

b=0

a=21

c=(-3k+7)

0-4*21*[-3k+7] ≥0

-84*-1[3k-7] ≥0

84*[3k-7] ≥0

3k-7 ≥0

3k ≥7

k ≥7/3