Range is all real numbers
(-infinity, positive infinity)
All it means is that a number equals itself, for example 5=5 (pretty obvious ik but it's that simple). Remember it by thinking that a number would look into the mirror and see itself in its reflection (kinda sounds like reflexive).
Area of shaded area= area of large rectangle-area of small rectangle
=(2x+a)(2x)-x(x+b)
=4x^2+2xa-x^2-bx
=3x^2+2xa-bx
=3x^2+2x-4x
=3x^2-2x+0
Whats the question that you have and remember theres always google
7/11 in decimal form rounded to the nearest thousandth is : 0.636
