Tickbox Quiz #9, Question 12 (I'm overwhelmed plan)

GRE Quant Problem Solving
1

In question 12, the equation is y=|x(squared) + 9x| +d. Why does Greg break it into two equations of

  1. 0=x(squared) +9x - d and 0=x(squared)+9x+d?

Based on the videos and quant mountain, shouldn’t it be 0=x(squared)+9x+d and 0= -x(squared) -9x+d?
I’m confused as to why the “d” is changing when it is outside of the absolute value symbol as well as why he is not making the 2nd equation negative for the terms within the absolute value.

2

What you wrote and what greg wrote are actually the same thing.

Factoring out a -1 makes it identical to your second equation