How do you factorise 14xy-21x plus 7?

14xy - 21x + 7

'7' is a common factor to all three coefficients. So 'take it out'.

Hence

7(2xy - 3x + 1)

The rest of it , inside the brackets does not factor.

However, I suspect the 'y' should be a 'power of 2'

Hence

7(2x^(2) - 3x + 1)

This factors to

7(2x - 1)(x - 1) Fully factored.!!!!