Answer:
x=10.75 in
Step-by-step explanation:
A = 390 = x(3x+4)
3x²+4x-390 =0
ax²+bx+c=0
x= (-b±√b²-4ac)/2a
x= (-4±√(16+4680))/6 = (-4±2√1174)/6 = (-2±√1174)/3
We will consider only the x that gives us a positive answer because the dimensions cannot be negative.
x= (-2+√1174)/3 = 10.75456113≈ 10.75
