Question

Plz help and explain

Answer 1

To solve this problem, we need to first find the dimensions of the side of the blue and purple squares.

We're given that the purple (smaller) square has a side length of x inches.
We are also given that the blue band has a width of 5 inches.
Since the blue band surrounds the purple square on both sides, the length of the blue square is x+2(5)=x+10 inches.

The net area of the band is therefore the difference of the area of the blue square and the purple square, namely take out the area of the purple square from the blue.

Therefore
Area of band
$=(x+10)^2-x^2$    [recall $(a+b)^2=a^2+2ab+b^2$
$=x^2+20x+100-x^2$
$=20x+100$   or 20(x+5)  if you wish.