x^2+15x-2

You have it the wrong way around DDS

 

It has to multiply to -2 and add to 15.

There are no rational number that fit this description.

x^2+15x-2

 

x^2+15x-2 = (x+a)(x+b)

 

a plus b makes -2

a times b makes 15

 

a = -5 and b = -3

 

if (x+a)(x+b) = 0

either (x+a) = 0 or (x+b) = 0

so (x+-5) = 0 or (x+-3) = 0

or x is either 5 or 3