Question 288724
10*8=80 cm^2 is the area of the picture.
(10+2x)(8+2x)-80=80
80+16x+20x+4x^2-160=0
4x^2+36x-80=0
4(x^2+9x-20)=0
{{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}}
x=(-9+-sqrt[9^2-4*1*-20])/2*1
x=(-9+-sqrt[81+80])/2
x=(-9+-sqrt161)/2
x=(-9+-12.69)/2
x=(-9+-12.69)/2
x=(-9+12.69)/2
x=3.69/2
x=1.8 cm. is the width of the mat.
Proof:
(10+2*1.8)(8+2*1.8)-80=80
(10+3.6)(8+3.6)=160
13.8*11.6=160
160~160