The area of the regular pentagon is 6.9 cm2. what is the perimeter? 2 cm 5 cm 10 cm 20 cm

As the regular pentagon there is 5 regular triangles.

And the area of 1 regular triangle is:

At = Side^2 × √(3)/4

But, as the pentagon has 5 triangle

Then,

Ap = 5 × Side^2 . √(3)/4

Replacing Ap = 6.9

5 × Side^2 . √(3)/4 = 6.9

Side^2 . √(3)/4 = 6.9 ÷ 5

Side^2 . √(3) = 4 × 1,38

Side^2 = 5,52 ÷ √(3)

Side^2 = 3,187

Side = √(3,187)

Side = 1,785 cm

Then,

The total perimeter will be:

P = 5 × Side

P = 5 × 1,785

P = 8,92 cm

Well, I did find this answer.

The answer would be a

First subtract 10 from both side
y^2+6y-16=0
(y+8)(y-2)=0
-8 and 2