Question 74085
Given a Triangle whose three sides are:
.
3x+7
4x-9 and
5x+6
.
The problem is to find a polynomial that represents the perimeter.  By definition the perimeter
of a triangle is the sum of the lengths of the 3 sides.  So all you have to do here is 
to add
the three sides together.  When you do you get:
.
3x + 7 + 4x - 9 + 5x + 6
.
Rearrange the terms so that all the terms that have an x in them are together and all
the numbers are together.  Now add all the terms having an x to get that 3x + 4x + 5x = 12x. 
Put 12x into the expression as a replacement for 3x + 4x + 5x.  When you do the equation
becomes:
.
12x + 7 - 9 + 6
.
Now add all the numbers together.  Watch out for the signs this time because one of the
numbers has a minus sign.  +7 and +6 add to make 13 and then you add -9 which is the same as
subtracting 9 from 13 to get 4.  Replace the three numbers with 4 and the answer to this 
problem becomes:
.
12x + 4
.
This is the polynomial that represents the perimeter of the triangle having the sides given 
in the problem.
.
Hope this helps you to see what is going on in this problem.  Just understand the definition
of the word "perimeter", then add the sides algebraically, and finally combine like terms.
That's all you have to do.