Question

I just don't get how (a+1)b-3(a+1)=(a+1)(b-3) , I know you must use the distributive law but I don't know how

Answer 1

since (a+1) appears in 'both places' it can be factored out of the equation and what is left is b-3.

it can only happen when the EXACT sequence can be found more than once (if one of them had been (a-1) you couldnt factor it out.

Answer 2

ow I get it you just can let one away when you 2 times the same sequence :) thank you very much

Answer 3

Seems like you've got this under control.
Here's a visual representation if it helps though. :)

\[\Large \left[\color{orangered}{(a+1)b}-\color{royalblue}{3(a+1)}\right]\]When we factor (a+1) out of each term we get:\[\Large (a+1)\left[\color{orangered}{b}-\color{royalblue}{3}\right]\]