Answer:
I think you multiply 4 by 5 ft
its 30 because if you add the numbers together then you get 90, then you do 180-90 and get 90, divide 90 by 3 and get 30
You can re-write this quotient this way :

What's inside the square root must be greater than or equal to 0, because the domain of the square root function is defined on R+ (which is [0,+∞))
In other word we must find x so that :

at the end we get
28(x-1) ≥ 0
28x - 28 ≥ 0
28x ≥ 28
x ≥ 1
So the answer is B, x ≥ 1
<span>If x= side of the square, and A = area of square, then
A = x^2
dA/dx = 2x, or
dA = 2x*dx, where dx is the differential in x (same as error)
dA/A = 2x*dx/(x^2) = 2*dx/x = 2*(0.05cm)/(15cm) = 0.00667 = 0.667%
for b):
if dA/A = 0.025 = 2*dx/x, then
dx/x=(0.025)/2 = 0.0125 = 1.25 %
I hope I helped. :)</span>