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

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 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).

Ok, I got it now, I dont know what I was thinking. Thanks 🙂

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

Hope you are never plotting a course for a plane I'm on.

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

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. 😛

i hope the buttons are not plus or minus buttons lols

thanks for the laugh

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. 😛

press a wrong button, how do you know you're not flying off into oblivion?

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.

Especially if you are in a plane.

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.

Slow learner.

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

Umm...are you telling us it's ok that you're a pilot even though driving is too difficult for you?

Originally posted by Gastel
Slow learner.

I was busy studying philosophy.

Originally posted by Bowmann
I was busy studying philosophy.

"studying"? "philosophy"? oxymoron?