Respuesta :
Refer to the attached image.
Let the width of the border be 'x' inch.
Area of border = Area of rectangle ABCD - Area of rectangle PQRS
Area of rectangle ABCD = [tex]length \times width[/tex]
= [tex]AB \times BC[/tex]
= [tex](13+2x) \times (9+2x)[/tex] square units.
Area of rectangle PQRS = [tex]PQ \times RQ[/tex]
= [tex]13 \times 9[/tex]
= 117 square units.
So, area of border = [tex](13+2x)(9+2x)-117 = 48[/tex]
As it is given that the area of border is 48 square units.
So, [tex]117+26x+18x+4x^2-117 = 48[/tex]
[tex]44x + 4x^2-48=0[/tex]
[tex]4x^2 + 44x = 48[/tex]
So, the complete equation is [tex]4x^2 + 44x = 48[/tex].
Now, we will find 'x' in the equation [tex]x^2+11x-12=0[/tex],
[tex]x^2 + 12x - x -12 =0[/tex]
[tex]x(x+12)-1(x+12)=0[/tex]
(x-1) (x+12)=0
So, x = 1 or x = -12
Width can'not be negative.
So, x = 1 .
Therefore, the width of the border can'not be 2.5 inch.
Therefore, the width of the border is 1 inch.
