Write a quadratic function in standard form that has 2 solutions - 4 & 5

The sum of the roots is - 4+5=1 and the product is - 4*5=-20. The x coefficient of a quadratic with leading coefficient 1 is the negative sum of the roots or - 1 and the constant term of this quadratic is the product of the roots or 20. The quadratic is then x^2-x+20.