Look at the +y and -2. Do you see how the +y is actually a (1)y? Because anything multiplied by 1 is itself. What you probably don't know is that when you factor, the -2 and +1 in (3y-2)(y+1), has to add up to +1, because when you distribute it out, thats the only way "y" can have a (1) in front of it.

Take a look at what 3y distributes to. (3y-2)(y+1). If you just distribute the 3y, you get 3y^2 + 3y. If you distribute the -2, you get -2y-2. See how the "y"s add up and make (1)y?

Basically, to factor that, you take out a (3y____________) leave some space, then multiply that to (y_______) because 3y*y = 3y^2. Thats the first part. Then you figure out what two numbers added together would make 1, because it is (1)y when you distribute it out. But 3y multiplies to the 1, like I showed you above. So, What added to 3y makes 1y? -2y!! So what are the coefficients? 1 and -2

So you get (3y - 2)(y + 1). It wouldn't work the other way, because then 3y would multiply into the -2
Does -6y + 1y = +y? No.

(3y + 1)(y - 2) = 3y^2 - 6y + y - 2 = 3y^2 - 5y - 2.
See?
Hope this helps!

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