## Help Simplifying an Equation

Simplificatation, evaluation, linear equations, linear graphs, linear inequalities, basic word problems, etc.

### Help Simplifying an Equation

Hi,
I'm trying to figure out how they simplified this:
$[a_1 + d]+[a_1+(n-2)d]$

to this:
$2a_1 + (n-1)d$

I get how the two $a_1$s get to $2a_1$ but I can't figure out how they're getting the two $d$s two just one.

Help?

mb
maroonblazer

Posts: 50
Joined: Thu Aug 12, 2010 11:16 am

maroonblazer wrote:I'm trying to figure out how they simplified this:
$[a_1 + d]+[a_1+(n-2)d]$

to this:
$2a_1 + (n-1)d$

What did you get when you multiplied out the second bit? You got to here:

. . . . .$a_1\, +\, d\, +\, a_1\, +\, nd\, -\, 2d$

. . . . .$a_1\, +\, a_1\, +\, nd\, +\, 1d\, -\, 2d$

...and then what?

stapel_eliz

Posts: 1784
Joined: Mon Dec 08, 2008 4:22 pm

### Re: Help Simplifying an Equation

Ahhh...

$2a_1+nd-1d = 2a_1+(n-1)d$

Thank you!
maroonblazer

Posts: 50
Joined: Thu Aug 12, 2010 11:16 am