7x – 6x² + 20 = - 6x² + 7x + 20

Here, coefficient of x² = -6, coefficient of x = 7and constant term = 20

We shall now split up the coefficient of x i.e., 7 into two parts whose sum is 7 and product is -6 * 20 = - 120

Clearly,

15 - 8 = 7 and,

15 (-8) = - 120

So, we write middle term 7x as 15x - 8x

Thus, we have

-6x² + 7x + 20 = -6x² + 15x - 8x + 20

= -3x (2x – 5) - 4 (2x – 5)

= - (3x + 4) (2x - 5)