Question

Question #93719

Answer 1

`(x+5)(x-3)=color(green)(x^2+2x-15)`

Explanation:

I don't know which "formula" you mean, so I will use:
`color(white)("XXX")(x+color(red)a)(x+color(blue)b)=x^2+(color(red)a+color(blue)b)+color(red)acolor(blue)b`
with `color(red)a=color(red)(+5)` and `color(blue)b=color(blue)(-3)`

`(x+color(red)((+5)))(x+color(blue)((-3)))=x^2+(color(red)((+5))+color(blue)((-3)))x+(color(red)((+5)) * color(blue)((-3)))`

`color(white)("XXXXXXXXXXXXXX")=x^2+2x-15`