q*L^4/8AB-R*L^3/3AB=R/(AB/L^3) 如何算出R=3qL/2?

Sol
QL^4/(8AB)－R*L^3/(3AB)=R/(AB/L^3)
QL^4/(8AB)－R*L^3/(3AB)=RL^3/(AB)
(24AB/L^3)[Q*L^4/(8AB)－R*L^3/(3AB)]=(24AB/L^3)RL^3/(AB)
24[QL/8－R/3]=24R
3QL－8R=24R
3QL=32R
R=3QL/32

Q(L^4)/(8AB)-R(L^3)/(3AB)=R/(AB/L^3)
3Q(L^4)/(24AB)-8R(L^3)/(24AB)=R(L^3)/(AB)
[3Q(L^4)-8R(L^3)]/24=R(L^3)
3QL-8R=24R
3QL=32R
R=3QL/32

Q*L^4/8AB-R*L^3/3AB = R/(AB/L^3)
Q*L^4/8AB = R*L^3/AB +1/3(R*L^3/AB)
Q*L^4/8AB = 4/3(R*L^3/AB)
L^3/AB(Q*L/8) = L^3/AB(4/3)R
Q*L/8 = (4/3)R
∴ R=3QL/32

# [你的答案：R=3qL/2 , 是 分母漏了個 3 字嗎?]