Question

If one of the zero of x²-3kx+4k is twice the other. Find the value of k.

Answer 1

If alpha = 2 Beta,

alpha + beta = -b/a

3 beta = 3k (substituting both sides.)

Beta = K ......... ........ ....... (1)

(Alpha)(Beta) = c/a

(2Beta)(Beta) = 4k.

2Beta2 = 4k

Beta2 = 4k/2

Beta = root of (2k) ...... ........... .......... (2)

From 1 and 2,

k = root of (2k)

On squaring both sides,

K2 = 2K

K2/K = 2

Therefore, K = 2.