=====================================================
Explanation:
To factor this, we need to find two numbers that
Through trial and error, you would find that the two numbers are -2 and -7
-2*(-7) = 14
-2 + (-7) = -9
So that's why the given trinomial factors to (y-2)(y-7)
You can use the FOIL rule to go from (y-2)(y-7) back to y^2-9y+14 again.