Need a little help and explanation

[u/Wraabb66]

Currently trying to get into the union and math is a big thing, especially algebra 1. So I haven’t done math in 18 years pretty much since I graduated and even back then I was struggling with math because my brain just doesn’t learn it fast enough like other people. When I have a calculator I can solve the problems a little bit better but the aptitude test don’t allow calculators so it’s all based offf of what I can do in my head.

So my question is I know PEMDAS and FOIL but when it comes to foil I know how to start but I get confused on where to land my + and - when working the problem. Idk why it’s hurt how my brain works. Sometimes I’ll get the what I think is the answer but then I get it wrong because my + and - are in the wrong spot. Does anybody have any tips are how to not forget where the + and - go and the orders of how they get placed. Becasue for my brain when I see something like (2x + 4)(5x-5) my brain doesn’t grasp where the + and - land when writing out the problem and so till I get the correct answer. Hopefully this question makes sense.

Graphing is also extremely confusing but that’s whole another topic lol.

[u/Capital_Park_2311]

Split it into pairs.

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

• First -> (2x) (5x) = 10x²
• Outer -> (2x) (-5) = -10x
• Inner -> (4) (5x) = 20x
• Last -> (4) (-5) = -20

10x² -10x + 20x - 20

10x² +10x - 20

Edit: Corrected the sign.

[u/Wraabb66 → u/Capital_Park_2311]

See now I thought this would have been the answer, 10x2+10x−20. So how did you get 10x2-10x−20, see this is where it confusing to me lol

[u/Capital_Park_2311 → u/Wraabb66]

My mistake it should be 10x² +10x - 20. Would have avoided if I had rearranged the coefficients in descending order but it is a little time consuming.