Question

If 1 is a root of the equation
5x^{2} +kx -21 =0.
find the other root

Answer 1

x = - 4.2

Explanation:

5 + k - 21 = 0

k - 16 = 0

k = 16

5x² + 16x - 21 = 0

discriminant = 256 - 4( 5 · -21)

256 - 4 (-105)

256 + 420

676

x = (- 16 + 26)/10

x = 10/10

x = 1

x = (-16-26)/10

x = -42/10

x = -4.2