WAEC - Mathematics (2015 - No. 1)
If {X: 2 d- x d- 19; X integer} and 7 + x = 4 (mod 9), find the highest value of x
2
5
15
18
설명
use trial and error method,
By substituting any of x = 2, 5, 15, 18 into 7 + x = 4 (mod 9)
any value of x that gives 7 + x = 4 (mod 9) is the correct value of x
In this case, x = 15.