If (x -1)2 = 400, which of the following could b the value of x-5 ?

If (x -1)² = 400, which of the following could b the value of x-5 ?

A 15

B 14

C -24

D -25

Correct Answer: Option C

(x -1)2 = 400

or, (x -1)2 = (20)2

or, (x -1) = (+-)20

or, x = (+-)20 + 1 = +21 or -19

Now,

x - 5 = +21 - 5 (Taking the positive value)

= +16

or,

x - 5 = -19 - 5 = -24