Solve 2xsquared plus 5x equals 5?

Answer 1

n! = n * (n-1) !

n!/n = n*(n-1)!/n //divid by n both sides

n!/n = (n-1)!

let n = 1

1!/1 = (1-1)!

1 = 0!

Hence proved that 0! = 1.