Which algebraic properties was applied to the expression a + (b + c) = (a + b) + c?

the Associative Property

Step-by-step explanation:

Notice that the ORDER doesn't change -- a, b, c on both sides.  But the GROUPING changes.

Example:

3 + (4 + 5) = (3 + 4) + 5

3 + 9 = 7 + 5

12 = 12

Subtraction does NOT behave this way!

8 - (7 - 1) = 8 - 6 = 2

(8 - 7) - 1 = 1 - 1 = 0

It matters who you associate with!  :-)

where is the figure

2x^2+5x+17

your welcome. : )