how to slove the congruence such that
cheers!
I think you've mistyped there. Should be 'so x = -1,1'
But -1 = 4 mod 5 so the answer is x = 1 and 4.
Test this by putting the values into .
x=0 gives 0-1 = -1 = 4 mod 5 (since -1 + 5 = 5)
x=1 gives 1-1 = 0.
x=2 gives 4-1 = 3.
x=3 gives 9-1 = 8 = 3 mod 5 (since 8 - 3 = 5)
x=4 gives 16-1 = 15 = 0 mod 5 (since 15 - 5 - 5 - 5 = 0)
This confirms that 1 and 4 are the correct answers.