Question

If 4x^2 + kx + 25 = 0 has exactly one solution, what could be the value of k?

Answer 1

discriminant should be 0
k^2-4*4*25=0
k^2=400
k=+-20

Answer 2

u can also cross check when k=20
then 4x^2 + kx + 25 = 0 reduces to (2x+5)^2
when k=-20
then 4x^2 + kx + 25 = 0 reduces to (2x-5)^2