Math Question

I know this is not the place to ask math questions, but since Im doing an online math class, Its hard for me to ask a real person.

In my Math textbook, Im having a hard time understanding this problem, I know its something simple, I just cant figure out what. The fact that Im dum at math isnt helping any.

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


This is how the book says to simplify.
-2(x-5)+ 4(2x + 2) = -2*x + (-2)(-5) + 4*2x + 4/2
= -2x + 10 + 8x +8
= 6x + 18


This is how it seems to me it should go, which gives it a totaly different answer.
-2(x-5)+ 4(2x + 2) = -2*x -(-2)(-5) + 4*2x + 4/2
= -2x - 10 + 8x +8
= -2x + (-10) + 8x +8
= 6x + (-2) or = 6x - 2

So what am I doing wrong? Why are they changing the minus sign to a plus sign when they are caculating, for no reason at all?

* = mutiply

Originally posted by flyUnity
This is how it seems to me it should go, which gives it a totaly different answer.
-2(x-5)+ 4(2x + 2) = -2*x -(-2)(-5) + 4*2x + 4/2
= -2x - 10 + 8x +8
= -2x + (-10) + 8x +8
= 6x + (-2) or = 6x - 2

So what am I doing wrong? Why are they changing the minus sign to a plus sign when they are caculating, for no reason at all?

* = mutiply

Originally posted by Coconut
your problem is in the first distribution. The -2 needs to go to the x, which you did right, but also to the -5, and (-2)*(-5) is (+10).

Originally posted by flyUnity
Ok, I got it now, I dont know what I was thinking. Thanks 🙂

Originally posted by XanthosNZ
Hope you are never plotting a course for a plane I'm on.

Originally posted by flyUnity
Dont worry, Computers plot my courses now. They give me headings, bearings, relative winds, and magnetic error variations all with with only pressing a few buttons on the computer. 😛

Originally posted by flyUnity
Dont worry, Computers plot my courses now. They give me headings, bearings, relative winds, and magnetic error variations all with with only pressing a few buttons on the computer. 😛

Hey, Im not that dumb. Flying is easier then driving a car.

Originally posted by flyUnity
Hey, Im not that dumb. Flying is easier then driving a car.

I learnt that a minus times a minus is a plus when I was four months old.

Originally posted by Bowmann
I learnt that a minus times a minus is a plus when I was four months old.

Originally posted by flyUnity
Hey, Im not that dumb. Flying is easier then driving a car.

Originally posted by Gastel
Slow learner.

Originally posted by Bowmann
I was busy studying philosophy.