Answer:
8 feet
Step-by-step explanation:
Given data
Area= 64 square feet
Base= x feet
Height= x+8 feet
The expression for the area
A= 1/2b*h
substitute
64= 1/2*x*(x+8)
64= 1/2*x^2+8x
64= (x^2+8x)/2
cross multiply
64*2= x^2+8x
128= x^2+8x
rearrange
x^2+8x-128= 0
using the quadratic formula
a=1
b=8
c=-128
x= -b±√b^2-4ac/2a
x= -1±√8^2-4*1*-128/2*1
simplifying
x= 8
x=-16
Hence the height of the base is
h= 8 feet